diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..876174e
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1 @@
+/phpcs.xml.dist export-ignore
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 0000000..6dad948
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,37 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - "master"
+  workflow_dispatch:
+
+jobs:
+  tests:
+    name: PHP ${{ matrix.php }}
+    runs-on: ubuntu-22.04
+    strategy:
+      fail-fast: false
+      matrix:
+        php:
+          - "8.3"
+          - "8.4"
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+        env:
+          phpts: ${{ matrix.phpts }}
+
+      - name: "Install dependencies with Composer"
+        uses: "ramsey/composer-install@v3"
+        with:
+          composer-options: "--prefer-dist"
+
+      - name: Run PHPUnit tests
+        run: composer test
diff --git a/.gitignore b/.gitignore
index 7579f74..105fc17 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,4 @@
-vendor
+.phpunit.cache
 composer.lock
+phpunit.xml
+vendor
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
new file mode 100644
index 0000000..3c54c19
--- /dev/null
+++ b/phpunit.xml.dist
@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         colors="true"
+         cacheDirectory=".phpunit.cache"
+         displayDetailsOnTestsThatTriggerWarnings="true"
+         displayDetailsOnTestsThatTriggerErrors="true"
+         displayDetailsOnTestsThatTriggerDeprecations="true"
+         displayDetailsOnTestsThatTriggerNotices="true"
+         failOnEmptyTestSuite="true"
+>
+    <testsuites>
+        <testsuite name="DS Tests">
+            <directory>tests</directory>
+        </testsuite>
+    </testsuites>
+</phpunit>
diff --git a/tests/CollectionTest.php b/tests/CollectionTestCase.php
similarity index 91%
rename from tests/CollectionTest.php
rename to tests/CollectionTestCase.php
index 8ecb063..e81b5f9 100644
--- a/tests/CollectionTest.php
+++ b/tests/CollectionTestCase.php
@@ -10,7 +10,7 @@
 use function strpos;
 use function var_dump;
 
-abstract class CollectionTest extends TestCase
+abstract class CollectionTestCase extends TestCase
 {
     /**
      * Sample sizes.
@@ -18,10 +18,15 @@ abstract class CollectionTest extends TestCase
     const MANY = 65;
     const SOME = 17;
 
+    /**
+     * Create an instance of the data structure being tested.
+     */
+    abstract public static function getInstance(array $values = []);
+
     /**
      * Generic mixed value sample array.
      */
-    public function sample()
+    public static function sample()
     {
         return array_merge(
             [[]],                               // empty
@@ -38,23 +43,23 @@ public function sample()
     /**
      * @return array provides two equal values for each test.
      */
-    public function basicDataProvider()
+    public static function basicDataProvider()
     {
         $values = [
             [],
             ['a'],
             ['a', 'b'],
             ['a', 'b', 'c'],
-            $this->sample(),
+            self::sample(),
         ];
 
-        return array_map(function($a) { return [$a, $a]; }, $values);
+        return array_map(fn($a) => [$a, $a], $values);
     }
 
     /**
      * @return array a data provider for Sequence and Set to test out of range.
      */
-    public function outOfRangeDataProvider()
+    public static function outOfRangeDataProvider()
     {
         return [
             [[ ], -1],
@@ -64,7 +69,7 @@ public function outOfRangeDataProvider()
         ];
     }
 
-    public function badIndexDataProvider()
+    public static function badIndexDataProvider()
     {
         return [
             [[], 'a'],
@@ -250,7 +255,7 @@ protected function cleanVarDump($expression)
      */
     public function testConvertingToBoolean()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertTrue((bool) $instance);
     }
 }
@@ -268,9 +273,9 @@ public function __construct($test) {
         $this->test = $test;
     }
 
-    public function getInstance(array $values = null)
+    public function getInstance(array|null $values = null)
     {
-        return $this->test->getInstance($values);
+        return $this->test::getInstance($values);
     }
 }
 
diff --git a/tests/Deque/__construct.php b/tests/Deque/__construct.php
index 8643abb..7b6f1b2 100644
--- a/tests/Deque/__construct.php
+++ b/tests/Deque/__construct.php
@@ -1,33 +1,31 @@
 <?php
 namespace Ds\Tests\Deque;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 use Ds\Deque;
 
 trait __construct
 {
-    public function constructDataProvider()
+    public static function constructDataProvider()
     {
         return array_map(function($a) { return [$a, $a]; }, [
             [],
             ['a'],
             ['a', 'b'],
             ['a', 'b', 'c'],
-            $this->sample(),
+            self::sample(),
             range(1, self::MANY),
         ]);
     }
 
-    /**
-     * @dataProvider constructDataProvider
-     */
+    #[DataProvider('constructDataProvider')]
     public function testConstruct($values, array $expected)
     {
         $this->assertToArray($expected, new Deque($values));
     }
 
-   /**
-     * @dataProvider constructDataProvider
-     */
+   #[DataProvider('constructDataProvider')]
     public function testConstructUsingNonArrayIterable(array $values, array $expected)
     {
         $this->assertToArray($expected, new Deque(new \ArrayIterator($values)));
diff --git a/tests/Deque/allocate.php b/tests/Deque/allocate.php
index 5aceb38..2529f47 100644
--- a/tests/Deque/allocate.php
+++ b/tests/Deque/allocate.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Deque;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait allocate
 {
-    public function allocateDataProvider()
+    public static function allocateDataProvider()
     {
         $m = \Ds\Deque::MIN_CAPACITY;
 
@@ -22,12 +24,10 @@ public function allocateDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider allocateDataProvider
-     */
+    #[DataProvider('allocateDataProvider')]
     public function testAllocate(int $initial, int $allocate, int $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->allocate($initial);
         $instance->allocate($allocate);
diff --git a/tests/Deque/capacity.php b/tests/Deque/capacity.php
index 4ba6da1..571afda 100644
--- a/tests/Deque/capacity.php
+++ b/tests/Deque/capacity.php
@@ -7,7 +7,7 @@ public function testCapacity()
     {
         $min = \Ds\Deque::MIN_CAPACITY;
 
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertEquals($min, $instance->capacity());
 
         for ($i = 0; $i < $min; $i++) {
@@ -42,7 +42,7 @@ public function testAutoTruncate()
             0  =>   8,
         ];
 
-        $instance = $this->getInstance(range(1, array_keys($boundaries)[0]));
+        $instance = static::getInstance(range(1, array_keys($boundaries)[0]));
 
         for (;;) {
             if ( ! is_null(($expected = $boundaries[$instance->count()] ?? null))) {
@@ -61,7 +61,7 @@ public function testClearResetsCapacity()
     {
         $min = \Ds\Deque::MIN_CAPACITY;
 
-        $instance = $this->getInstance(range(1, self::MANY));
+        $instance = static::getInstance(range(1, self::MANY));
         $instance->clear();
         $this->assertEquals($min, $instance->capacity());
     }
diff --git a/tests/Deque/insert.php b/tests/Deque/insert.php
index 92140b7..bf7f6f3 100644
--- a/tests/Deque/insert.php
+++ b/tests/Deque/insert.php
@@ -9,7 +9,7 @@ trait insert
      */
     public function testInsertExtended()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         // The head of the deque will wrap around if all items are unshifted.
 
@@ -32,7 +32,7 @@ public function testInsertExtended()
 
     public function testInsertingIntoAnIsland()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         // It's possible that the head of the deque comes before the tail, but
         // is not at zero. This could overflow the buffer.
@@ -59,7 +59,7 @@ public function testInsertingIntoAnIsland()
 
     public function testInsertAtBoundaryWithMoreOnTheLeft()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->push(3, 4, 5, 6);
         $instance->unshift(1, 2);
 
@@ -74,7 +74,7 @@ public function testInsertAtBoundaryWithMoreOnTheLeft()
 
     public function testInsertAtBoundaryWithMoreOnTheRight()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->push(5, 6);
         $instance->unshift(1, 2, 3, 4);
 
@@ -89,7 +89,7 @@ public function testInsertAtBoundaryWithMoreOnTheRight()
 
     public function testInsertAtBoundaryWithEqualOnBothSides()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->push(4, 5, 6);
         $instance->unshift(1, 2, 3);
 
@@ -103,7 +103,7 @@ public function testInsertAtBoundaryWithEqualOnBothSides()
 
     public function testAlmostFullInsertAtZero()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->push(...range(1, 6));
         $instance->insert(0, 0);
 
diff --git a/tests/Deque/remove.php b/tests/Deque/remove.php
index 954f436..f33d077 100644
--- a/tests/Deque/remove.php
+++ b/tests/Deque/remove.php
@@ -9,7 +9,7 @@ trait remove
      */
     public function testRemoveExtended()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         /* HEAD WRAPPED AROUND, TAIL = 0 */
         // The head of the deque will wrap around if all items are unshifted.
@@ -25,7 +25,7 @@ public function testRemoveExtended()
         $this->assertTrue($instance->isEmpty());
 
         /* HEAD WRAPPED AROUND, TAIL > 0 */
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->unshift('b'); // [_, _, ..., _, b] tail = 0, head = 3
         $instance->unshift('a'); // [_, _, ..., a, b] tail = 0, head = 2
@@ -38,7 +38,7 @@ public function testRemoveExtended()
         $this->assertTrue($instance->isEmpty());
 
         /* HEAD NOT WRAPPED, TAIL > 0 */
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->push('a'); // [a, _, _, ..., _] tail = 1, head = 0
         $instance->push('b'); // [a, b, _, ..., _] tail = 2, head = 0
diff --git a/tests/Deque/slice.php b/tests/Deque/slice.php
index 458a3bf..47143d8 100644
--- a/tests/Deque/slice.php
+++ b/tests/Deque/slice.php
@@ -9,7 +9,7 @@ trait slice
      */
     public function testSliceExtended()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->unshift('c'); // [_, _, _, _, _, _, _, c] tail = 0, head = 7
         $instance->unshift('b'); // [_, _, _, _, _, _, b, c] tail = 0, head = 6
@@ -30,7 +30,7 @@ public function testSliceExtended()
         /* If only some values have wrapped around, slice would have to copy
            from both the wrapped and not-wrapped values */
 
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->push('b');    // [b, _, _, _, _, _, _, _] tail = 1, head = 0
         $instance->push('c');    // [b, c, _, _, _, _, _, _] tail = 2, head = 1
diff --git a/tests/DequeTest.php b/tests/DequeTest.php
index 11f3c19..f432578 100644
--- a/tests/DequeTest.php
+++ b/tests/DequeTest.php
@@ -3,7 +3,7 @@
 
 use ArrayAccess;
 
-class DequeTest extends CollectionTest
+class DequeTest extends CollectionTestCase
 {
     use Sequence\_clone;
     use Sequence\_echo;
@@ -54,14 +54,14 @@ class DequeTest extends CollectionTest
     use Sequence\toArray;
     use Sequence\unshift;
 
-    public function getInstance(array $values = [])
+    public static function getInstance(array $values = [])
     {
         return new \Ds\Deque($values);
     }
 
     public function testReallocatingWhenHeadNotAtZero()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->push('a', 'b', 'c', 'd');
         $instance->shift();
@@ -81,7 +81,7 @@ public function testReallocatingWhenHeadNotAtZero()
 
     public function testReallocatingWhenHeadHasWrapped()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->push('a');
         $instance->push('b');
@@ -106,7 +106,7 @@ public function testReallocatingWhenHeadHasWrapped()
 
     public function testRealignmentOfWrappedBufferWithLargeTempSpace()
     {
-        $instance = $this->getInstance();   // [_, _, _, _, _, _, _, _]
+        $instance = static::getInstance();   // [_, _, _, _, _, _, _, _]
 
         $instance->push('c', 'd');
         $instance->unshift('a', 'b');       // [c, d, _, _, _, _, a, b]
@@ -132,7 +132,7 @@ public function testRealignmentOfWrappedBufferWithLargeTempSpace()
         // Also test the boundary case, where the number of wrapped values
         // equals the amount of free space in the buffer.
 
-        $instance = $this->getInstance();   // [_, _, _, _, _, _, _, _]
+        $instance = static::getInstance();   // [_, _, _, _, _, _, _, _]
 
         $instance->push('c', 'd', 'e', 'f');
         $instance->unshift('a', 'b');       // [c, d, e, f, _, _, a, b]
@@ -149,7 +149,7 @@ public function testRealignmentOfWrappedBufferWithLargeTempSpace()
         ////////////////////////////////////////////////////////////////
         // Also test for assurance when there isn't enough space.
 
-        $instance = $this->getInstance();   // [_, _, _, _, _, _, _, _]
+        $instance = static::getInstance();   // [_, _, _, _, _, _, _, _]
 
         $instance->push('c', 'd', 'e', 'f', 'g');
         $instance->unshift('a', 'b');       // [c, d, e, f, g, _, a, b]
@@ -166,6 +166,6 @@ public function testRealignmentOfWrappedBufferWithLargeTempSpace()
 
     public function testImplementsArrayAccess()
     {
-        $this->assertInstanceOf(ArrayAccess::class, $this->getInstance());
+        $this->assertInstanceOf(ArrayAccess::class, static::getInstance());
     }
 }
diff --git a/tests/Map/__construct.php b/tests/Map/__construct.php
index 7a4f5db..59fb280 100644
--- a/tests/Map/__construct.php
+++ b/tests/Map/__construct.php
@@ -1,32 +1,30 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 use Ds\Map;
 
 trait __construct
 {
-    public function constructDataProvider()
+    public static function constructDataProvider()
     {
         return array_map(function($a) { return [$a, $a]; }, [
             [],
             ['a' => 1],
             ['a' => 1, 'b' => 2],
             ['a' => 1, 'b' => 2, 'c' => 3],
-            $this->sample(),
+            self::sample(),
         ]);
     }
 
-    /**
-     * @dataProvider constructDataProvider
-     */
+    #[DataProvider('constructDataProvider')]
     public function testConstruct(array $values, array $expected)
     {
         $this->assertToArray($expected, new Map($values));
     }
 
-    /**
-     * @dataProvider constructDataProvider
-     */
+    #[DataProvider('constructDataProvider')]
     public function testConstructUsingNonArrayIterable(array $values, array $expected)
     {
         $this->assertToArray($expected, new Map(new \ArrayIterator($values)));
diff --git a/tests/Map/_clone.php b/tests/Map/_clone.php
index 58230a8..71ed9ef 100644
--- a/tests/Map/_clone.php
+++ b/tests/Map/_clone.php
@@ -1,19 +1,19 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _clone
 {
-    public function cloneDataProvider()
+    public static function cloneDataProvider()
     {
-        return $this->basicDataProvider();
+        return self::basicDataProvider();
     }
 
-    /**
-     * @dataProvider cloneDataProvider
-     */
+    #[DataProvider('cloneDataProvider')]
     public function testClone($values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $clone = clone $instance;
 
diff --git a/tests/Map/_echo.php b/tests/Map/_echo.php
index f5ed083..2e8af6b 100644
--- a/tests/Map/_echo.php
+++ b/tests/Map/_echo.php
@@ -5,6 +5,6 @@ trait _echo
 {
     public function testEcho()
     {
-        $this->assertInstanceToString($this->getInstance());
+        $this->assertInstanceToString(static::getInstance());
     }
 }
diff --git a/tests/Map/_empty.php b/tests/Map/_empty.php
index f2351c7..d47b3ba 100644
--- a/tests/Map/_empty.php
+++ b/tests/Map/_empty.php
@@ -1,10 +1,12 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _empty
 {
 
-    public function emptyDataProvider()
+    public static function emptyDataProvider()
     {
         // initial, key, empty
         return [
@@ -16,12 +18,10 @@ public function emptyDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider emptyDataProvider
-     */
+    #[DataProvider('emptyDataProvider')]
     public function testArrayAccessEmpty(array $initial, $key, bool $empty)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($initial as $key => $value) {
             $instance->put($key, $value);
@@ -30,12 +30,10 @@ public function testArrayAccessEmpty(array $initial, $key, bool $empty)
         $this->assertEquals($empty, empty($instance[$key]));
     }
 
-    /**
-     * @dataProvider emptyDataProvider
-     */
+    #[DataProvider('emptyDataProvider')]
     public function testArrayAccessEmptyByReference(array $initial, $key, bool $empty)
     {
-        $instance = $this->getInstance([$initial]);
+        $instance = static::getInstance([$initial]);
         $this->assertEquals($empty, empty($instance[0][$key]));
     }
 
diff --git a/tests/Map/_foreach.php b/tests/Map/_foreach.php
index 73b6820..8090749 100644
--- a/tests/Map/_foreach.php
+++ b/tests/Map/_foreach.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _foreach
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testForEach(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertForEach($expected, $instance);
     }
 }
diff --git a/tests/Map/_isset.php b/tests/Map/_isset.php
index 045e21a..b6637ad 100644
--- a/tests/Map/_isset.php
+++ b/tests/Map/_isset.php
@@ -1,10 +1,12 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _isset
 {
 
-    public function issetDataProvider()
+    public static function issetDataProvider()
     {
         // initial, key, isset
         return [
@@ -16,12 +18,10 @@ public function issetDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider issetDataProvider
-     */
+    #[DataProvider('issetDataProvider')]
     public function testArrayAccessIsset(array $initial, $key, bool $isset)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($initial as $key => $value) {
             $instance->put($key, $value);
@@ -30,12 +30,10 @@ public function testArrayAccessIsset(array $initial, $key, bool $isset)
         $this->assertEquals($isset, isset($instance[$key]));
     }
 
-    /**
-     * @dataProvider issetDataProvider
-     */
+    #[DataProvider('issetDataProvider')]
     public function testArrayAccessIssetByMethod(array $initial, $key, bool $isset)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($initial as $key => $value) {
             $instance->put($key, $value);
@@ -44,12 +42,10 @@ public function testArrayAccessIssetByMethod(array $initial, $key, bool $isset)
         $this->assertEquals($isset, $instance->offsetExists($key));
     }
 
-    /**
-     * @dataProvider issetDataProvider
-     */
+    #[DataProvider('issetDataProvider')]
     public function testArrayAccessIssetByReference(array $initial, $key, bool $isset)
     {
-        $instance = $this->getInstance([$initial]);
+        $instance = static::getInstance([$initial]);
         $this->assertEquals($isset, isset($instance[0][$key]));
     }
 }
diff --git a/tests/Map/_jsonEncode.php b/tests/Map/_jsonEncode.php
index 668f00f..9402832 100644
--- a/tests/Map/_jsonEncode.php
+++ b/tests/Map/_jsonEncode.php
@@ -1,19 +1,19 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _jsonEncode
 {
-    public function jsonEncodeDataProvider()
+    public static function jsonEncodeDataProvider()
     {
-        return $this->basicDataProvider();
+        return self::basicDataProvider();
     }
 
-    /**
-     * @dataProvider jsonEncodeDataProvider
-     */
+    #[DataProvider('jsonEncodeDataProvider')]
     public function testJsonEncode(array $initial, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals(json_encode((object) $expected), json_encode($instance));
     }
 }
diff --git a/tests/Map/_serialize.php b/tests/Map/_serialize.php
index a5ef876..c7e5dae 100644
--- a/tests/Map/_serialize.php
+++ b/tests/Map/_serialize.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _serialize
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testSerialize(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertSerialized($expected, $instance, true);
     }
 }
diff --git a/tests/Map/_unset.php b/tests/Map/_unset.php
index 905593f..f93b0cc 100644
--- a/tests/Map/_unset.php
+++ b/tests/Map/_unset.php
@@ -6,14 +6,14 @@ trait _unset
 
     public function testArrayAccessUnset()
     {
-        $instance = $this->getInstance(['a' => 1]);
+        $instance = static::getInstance(['a' => 1]);
         unset($instance['a']);
         $this->assertToArray([], $instance);
     }
 
     public function testArrayAccessUnsetByReference()
     {
-        $instance = $this->getInstance(['a' => [1]]);
+        $instance = static::getInstance(['a' => [1]]);
         unset($instance['a'][0]);
 
         $this->assertToArray(['a' => []], $instance);
diff --git a/tests/Map/_var_dump.php b/tests/Map/_var_dump.php
index 5f6f6a5..7a0e61c 100644
--- a/tests/Map/_var_dump.php
+++ b/tests/Map/_var_dump.php
@@ -1,11 +1,13 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 use Ds\Pair;
 
 trait _var_dump
 {
-    public function varDumpDataProvider()
+    public static function varDumpDataProvider()
     {
         // values, expected array repr
         return [
@@ -24,12 +26,10 @@ public function varDumpDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider varDumpDataProvider
-     */
+    #[DataProvider('varDumpDataProvider')]
     public function testVarDump(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertInstanceDump($expected, $instance);
     }
 }
diff --git a/tests/Map/allocate.php b/tests/Map/allocate.php
index 1da4801..e75f9f8 100644
--- a/tests/Map/allocate.php
+++ b/tests/Map/allocate.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait allocate
 {
-    public function allocateDataProvider()
+    public static function allocateDataProvider()
     {
         $m = \Ds\Map::MIN_CAPACITY;
 
@@ -22,12 +24,10 @@ public function allocateDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider allocateDataProvider
-     */
+    #[DataProvider('allocateDataProvider')]
     public function testAllocate(int $initial, int $allocate, int $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->allocate($initial);
         $instance->allocate($allocate);
diff --git a/tests/Map/apply.php b/tests/Map/apply.php
index ff76fe3..86ed868 100644
--- a/tests/Map/apply.php
+++ b/tests/Map/apply.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait apply
 {
-    public function applyDataProvider()
+    public static function applyDataProvider()
     {
         // values, callback
         return [
@@ -13,12 +15,10 @@ public function applyDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider applyDataProvider
-     */
+    #[DataProvider('applyDataProvider')]
     public function testApply(array $values, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $instance->apply($callback);
 
         $expected = array_map($callback, array_keys($values), $values);
@@ -27,7 +27,7 @@ public function testApply(array $values, callable $callback)
 
     public function testApplyCallbackThrowsException()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
 
         try {
             $instance->apply(function($value) {
@@ -43,7 +43,7 @@ public function testApplyCallbackThrowsException()
 
     public function testApplyCallbackThrowsExceptionLaterOn()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
 
         try {
             $instance->apply(function($key, $value) {
@@ -63,7 +63,7 @@ public function testApplyCallbackThrowsExceptionLaterOn()
 
     public function testApplyDoesNotLeakWhenCallbackFails()
     {
-        $instance = $this->getInstance([
+        $instance = static::getInstance([
             "a" => new \stdClass(),
             "b" => new \stdClass(),
             "c" => new \stdClass(),
diff --git a/tests/Map/capacity.php b/tests/Map/capacity.php
index 4b3bae2..fef5f48 100644
--- a/tests/Map/capacity.php
+++ b/tests/Map/capacity.php
@@ -9,7 +9,7 @@ public function testCapacity()
     {
         $min = Map::MIN_CAPACITY;
 
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertEquals($min, $instance->capacity());
 
         for ($i = 0; $i < $min; $i++) {
@@ -44,7 +44,7 @@ public function testAutoTruncate()
             0  =>  8,
         ];
 
-        $instance = $this->getInstance(range(1, array_keys($boundaries)[0]));
+        $instance = static::getInstance(range(1, array_keys($boundaries)[0]));
 
         for(;;) {
             if ( ! is_null(($expected = $boundaries[$instance->count()] ?? null))) {
@@ -61,7 +61,7 @@ public function testAutoTruncate()
 
     public function testClearResetsCapacity()
     {
-        $instance = $this->getInstance(range(1, self::MANY));
+        $instance = static::getInstance(range(1, self::MANY));
         $instance->clear();
         $this->assertEquals(Map::MIN_CAPACITY, $instance->capacity());
     }
diff --git a/tests/Map/clear.php b/tests/Map/clear.php
index 50c975e..bc76749 100644
--- a/tests/Map/clear.php
+++ b/tests/Map/clear.php
@@ -5,7 +5,7 @@ trait clear
 {
     public function testClear()
     {
-        $instance = $this->getInstance($this->sample());
+        $instance = static::getInstance(self::sample());
         $instance->clear();
 
         $this->assertToArray([], $instance);
diff --git a/tests/Map/copy.php b/tests/Map/copy.php
index 06cda7b..d2a8f77 100644
--- a/tests/Map/copy.php
+++ b/tests/Map/copy.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait copy
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testCopy(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $copy = $instance->copy();
 
         $this->assertEquals($instance->toArray(), $copy->toArray());
diff --git a/tests/Map/count.php b/tests/Map/count.php
index 75ae53c..737ca0b 100644
--- a/tests/Map/count.php
+++ b/tests/Map/count.php
@@ -5,13 +5,13 @@ trait count
 {
     public function testCount()
     {
-        $instance = $this->getInstance($this->sample());
-        $this->assertCount(count($this->sample()), $instance);
+        $instance = static::getInstance(self::sample());
+        $this->assertCount(count(self::sample()), $instance);
     }
 
     public function testCountEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertCount(0, $instance);
     }
 }
diff --git a/tests/Map/diff.php b/tests/Map/diff.php
index 3c2d88a..23299b1 100644
--- a/tests/Map/diff.php
+++ b/tests/Map/diff.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait diff
 {
-    public function diffDataProvider()
+    public static function diffDataProvider()
     {
         // Keys in A but not in B.
         // A, B, expected result
@@ -17,23 +19,19 @@ public function diffDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider diffDataProvider
-     */
+    #[DataProvider('diffDataProvider')]
     public function testDiff(array $a, array $b, array $expected)
     {
-        $a = $this->getInstance($a);
-        $b = $this->getInstance($b);
+        $a = static::getInstance($a);
+        $b = static::getInstance($b);
 
         $this->assertEquals($expected, $a->diff($b)->toArray());
     }
 
-    /**
-     * @dataProvider diffDataProvider
-     */
+    #[DataProvider('diffDataProvider')]
     public function testDiffWithSelf(array $a, array $b, array $expected)
     {
-        $map = $this->getInstance($a);
+        $map = static::getInstance($a);
 
         $this->assertEquals([], $map->diff($map)->toArray());
     }
diff --git a/tests/Map/filter.php b/tests/Map/filter.php
index 7b7bd72..08d3b7c 100644
--- a/tests/Map/filter.php
+++ b/tests/Map/filter.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait filter
 {
-    public function filterDataProvider()
+    public static function filterDataProvider()
     {
         // values, callback, expected
         return [
@@ -20,12 +22,10 @@ public function filterDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider filterDataProvider
-     */
+    #[DataProvider('filterDataProvider')]
     public function testFilter(array $values, callable $callback, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $filtered = $instance->filter($callback);
 
@@ -35,7 +35,7 @@ public function testFilter(array $values, callable $callback, array $expected)
 
     public function testFilterCallbackThrowsException()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $filtered = null;
 
         try {
@@ -53,7 +53,7 @@ public function testFilterCallbackThrowsException()
 
     public function testFilterCallbackThrowsExceptionLaterOn()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $filtered = null;
 
         try {
@@ -73,7 +73,7 @@ public function testFilterCallbackThrowsExceptionLaterOn()
 
     public function testFilterDoesNotLeakWhenCallbackFails()
     {
-        $instance = $this->getInstance([
+        $instance = static::getInstance([
             "a" => new \stdClass(),
             "b" => new \stdClass(),
             "c" => new \stdClass(),
@@ -99,7 +99,7 @@ public function testFilterWithoutCallable()
             "f" => 0,
         ];
 
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertToArray(array_filter($values), $instance->filter());
     }
 }
diff --git a/tests/Map/first.php b/tests/Map/first.php
index 75cdde4..3167279 100644
--- a/tests/Map/first.php
+++ b/tests/Map/first.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait first
 {
-    public function firstDataProvider()
+    public static function firstDataProvider()
     {
         // initial, returned
         return [
@@ -13,12 +15,10 @@ public function firstDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider firstDataProvider
-     */
+    #[DataProvider('firstDataProvider')]
     public function testFirst(array $initial, $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $first = $instance->first();
 
         $this->assertEquals($expected, [$first->key, $first->value]);
@@ -26,7 +26,7 @@ public function testFirst(array $initial, $expected)
 
     public function testFirstNowAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->first();
     }
diff --git a/tests/Map/get.php b/tests/Map/get.php
index b6158f3..7cf8319 100644
--- a/tests/Map/get.php
+++ b/tests/Map/get.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait get
 {
-    public function getDataProvider()
+    public static function getDataProvider()
     {
         // initial, key, expected
         return [
@@ -11,56 +13,54 @@ public function getDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider getDataProvider
-     */
+    #[DataProvider('getDataProvider')]
     public function testGet(array $initial, $key, $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($expected, $instance->get($key));
     }
 
     public function testGetDefault()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertEquals('a', $instance->get('?', 'a'));
     }
 
     public function testGetKeyNotFound()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectKeyNotFoundException();
         $instance->get('?');
     }
 
     public function testArrayAccessGet()
     {
-        $instance = $this->getInstance(['a' => 1]);
+        $instance = static::getInstance(['a' => 1]);
         $this->assertEquals(1, $instance['a']);
     }
 
     public function testArrayAccessGetByMethod()
     {
-        $instance = $this->getInstance(['a' => 1]);
+        $instance = static::getInstance(['a' => 1]);
         $this->assertEquals(1, $instance->offsetGet('a'));
     }
 
     public function testArrayAccessGetByReference()
     {
-        $instance = $this->getInstance(['a' => [1]]);
+        $instance = static::getInstance(['a' => [1]]);
         $this->assertEquals(1, $instance['a'][0]);
     }
 
     public function testArrayAccessGetKeyNotFound()
     {
-        $instance = $this->getInstance(['a' => 1]);
+        $instance = static::getInstance(['a' => 1]);
         $this->expectKeyNotFoundException();
         $instance['b'];
     }
 
     public function testArrayAccessGetNullCoalesce()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $obj = new \stdClass;
 
diff --git a/tests/Map/hasKey.php b/tests/Map/hasKey.php
index 6c5eff5..9e1972b 100644
--- a/tests/Map/hasKey.php
+++ b/tests/Map/hasKey.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait hasKey
 {
-    public function hasKeyDataProvider()
+    public static function hasKeyDataProvider()
     {
         // initial, key, has
         return [
@@ -13,18 +15,16 @@ public function hasKeyDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider hasKeyDataProvider
-     */
+    #[DataProvider('hasKeyDataProvider')]
     public function testHasKey(array $initial, $key, bool $has)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($has, $instance->hasKey($key));
     }
 
     public function testHasKeyAfterRemoveAndPut()
     {
-        $instance = $this->getInstance(['a' => 1]);
+        $instance = static::getInstance(['a' => 1]);
         $this->assertTrue($instance->hasKey('a'));
 
         $instance->remove('a');
diff --git a/tests/Map/hasValue.php b/tests/Map/hasValue.php
index 35ad935..39626d5 100644
--- a/tests/Map/hasValue.php
+++ b/tests/Map/hasValue.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait hasValue
 {
-    public function hasValueDataProvider()
+    public static function hasValueDataProvider()
     {
         // initial, value, expected
         return [
@@ -14,18 +16,16 @@ public function hasValueDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider hasValueDataProvider
-     */
+    #[DataProvider('hasValueDataProvider')]
     public function testHasValue(array $initial, $value, bool $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($expected, $instance->hasValue($value));
     }
 
     public function testHasValueAfterRemoveAndPut()
     {
-        $instance = $this->getInstance(['a' => 1]);
+        $instance = static::getInstance(['a' => 1]);
         $this->assertTrue($instance->hasValue(1));
 
         $instance->remove('a');
diff --git a/tests/Map/intersect.php b/tests/Map/intersect.php
index ad7a967..0ab3f8e 100644
--- a/tests/Map/intersect.php
+++ b/tests/Map/intersect.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait intersect
 {
-    public function intersectDataProvider()
+    public static function intersectDataProvider()
     {
         // Keys in A that are also in B.
         // A, B, expected result
@@ -16,23 +18,19 @@ public function intersectDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider intersectDataProvider
-     */
+    #[DataProvider('intersectDataProvider')]
     public function testIntersect(array $a, array $b, array $expected)
     {
-        $a = $this->getInstance($a);
-        $b = $this->getInstance($b);
+        $a = static::getInstance($a);
+        $b = static::getInstance($b);
 
         $this->assertEquals($expected, $a->intersect($b)->toArray());
     }
 
-    /**
-     * @dataProvider intersectDataProvider
-     */
+    #[DataProvider('intersectDataProvider')]
     public function testIntersectWithSelf(array $a, array $b, array $expected)
     {
-        $map = $this->getInstance($a);
+        $map = static::getInstance($a);
 
         $this->assertEquals($a, $map->intersect($map)->toArray());
     }
diff --git a/tests/Map/isEmpty.php b/tests/Map/isEmpty.php
index 93da609..d636de0 100644
--- a/tests/Map/isEmpty.php
+++ b/tests/Map/isEmpty.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait isEmpty
 {
-    public function isEmptyDataProvider()
+    public static function isEmptyDataProvider()
     {
         // values, is empty
         return [
@@ -12,18 +14,16 @@ public function isEmptyDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider isEmptyDataProvider
-     */
+    #[DataProvider('isEmptyDataProvider')]
     public function testIsEmpty(array $values, bool $isEmpty)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertEquals($isEmpty, $instance->isEmpty());
     }
 
     public function testIsNotEmptyAfterRemove()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertTrue($instance->isEmpty());
 
         $instance->put('a', 1);
diff --git a/tests/Map/keys.php b/tests/Map/keys.php
index 8f020cb..e084c2d 100644
--- a/tests/Map/keys.php
+++ b/tests/Map/keys.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait keys
 {
-    public function keysDataProvider()
+    public static function keysDataProvider()
     {
         return [
             [[], []],
@@ -12,12 +14,10 @@ public function keysDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider keysDataProvider
-     */
+    #[DataProvider('keysDataProvider')]
     public function testKeys(array $initial, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $keys = $instance->keys();
 
         $this->assertInstanceOf(\Ds\Set::class, $keys);
diff --git a/tests/Map/ksort.php b/tests/Map/ksort.php
index 3b18817..5e78870 100644
--- a/tests/Map/ksort.php
+++ b/tests/Map/ksort.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait ksort
 {
-    public function sortKeyDataProvider()
+    public static function sortKeyDataProvider()
     {
         return [
             [[
@@ -24,12 +26,10 @@ public function sortKeyDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider sortKeyDataProvider
-     */
+    #[DataProvider('sortKeyDataProvider')]
     public function testSortByKey(array $values)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $expected = $values;
         ksort($expected);
@@ -38,12 +38,10 @@ public function testSortByKey(array $values)
         $this->assertToArray($expected, $instance);
     }
 
-    /**
-     * @dataProvider sortKeyDataProvider
-     */
+    #[DataProvider('sortKeyDataProvider')]
     public function testSortByKeyUsingComparator(array $values)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $instance->ksort(function($a, $b) {
             return $b <=> $a;
diff --git a/tests/Map/ksorted.php b/tests/Map/ksorted.php
index dc1ef42..9e14b3b 100644
--- a/tests/Map/ksorted.php
+++ b/tests/Map/ksorted.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait ksorted
 {
-    public function sortedKeyDataProvider()
+    public static function sortedKeyDataProvider()
     {
         return [
             [[
@@ -24,12 +26,10 @@ public function sortedKeyDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider sortedKeyDataProvider
-     */
+    #[DataProvider('sortedKeyDataProvider')]
     public function testSortedByKey(array $values)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $expected = $values;
         ksort($expected);
@@ -38,12 +38,10 @@ public function testSortedByKey(array $values)
         $this->assertToArray($values, $instance);
     }
 
-    /**
-     * @dataProvider sortKeyDataProvider
-     */
+    #[DataProvider('sortKeyDataProvider')]
     public function testSortedByKeyUsingComparator(array $values)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $sorted = $instance->ksorted(function($a, $b) {
             return $b <=> $a;
diff --git a/tests/Map/last.php b/tests/Map/last.php
index aeed3bb..0283d6b 100644
--- a/tests/Map/last.php
+++ b/tests/Map/last.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait last
 {
-    public function lastDataProvider()
+    public static function lastDataProvider()
     {
         // initial, returned
         return [
@@ -13,12 +15,10 @@ public function lastDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider lastDataProvider
-     */
+    #[DataProvider('lastDataProvider')]
     public function testLast($initial, $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $last = $instance->last();
 
         $this->assertEquals($expected, [$last->key, $last->value]);
@@ -26,7 +26,7 @@ public function testLast($initial, $expected)
 
     public function testLastNotAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->last();
     }
diff --git a/tests/Map/map.php b/tests/Map/map.php
index 1e86cda..19fb832 100644
--- a/tests/Map/map.php
+++ b/tests/Map/map.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait map
 {
-    public function mapDataProvider()
+    public static function mapDataProvider()
     {
         // values, callback
         return [
@@ -17,12 +19,10 @@ public function mapDataProvider()
     }
 
 
-    /**
-     * @dataProvider mapDataProvider
-     */
+    #[DataProvider('mapDataProvider')]
     public function testMap(array $values, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $mapped = $instance->map($callback);
         $expected = array_map($callback, array_keys($values), $values);
@@ -33,7 +33,7 @@ public function testMap(array $values, callable $callback)
 
     public function testMapPreservesKeys()
     {
-        $instance = $this->getInstance(["speed" => 5]);
+        $instance = static::getInstance(["speed" => 5]);
 
         $mapped = $instance->map(function ($key, $value) {
             return $value * 2;
@@ -44,7 +44,7 @@ public function testMapPreservesKeys()
 
     public function testMapCallbackThrowsException()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $mapped = null;
 
         try {
@@ -62,7 +62,7 @@ public function testMapCallbackThrowsException()
 
     public function testMapCallbackThrowsExceptionLaterOn()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $mapped = null;
 
         try {
@@ -82,7 +82,7 @@ public function testMapCallbackThrowsExceptionLaterOn()
 
     public function testMapDoesNotLeakWhenCallbackFails()
     {
-        $instance = $this->getInstance([
+        $instance = static::getInstance([
             "a" => new \stdClass(),
             "b" => new \stdClass(),
             "c" => new \stdClass(),
diff --git a/tests/Map/merge.php b/tests/Map/merge.php
index 2dae7cd..d195817 100644
--- a/tests/Map/merge.php
+++ b/tests/Map/merge.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait merge
 {
-    public function mergeDataProvider()
+    public static function mergeDataProvider()
     {
         // A, B, expected
         return [
@@ -16,23 +18,19 @@ public function mergeDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider mergeDataProvider
-     */
+    #[DataProvider('mergeDataProvider')]
     public function testMerge(array $initial, array $values, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $this->assertToArray($expected, $instance->merge($values));
         $this->assertToArray($initial, $instance);
     }
 
-    /**
-     * @dataProvider mergeDataProvider
-     */
+    #[DataProvider('mergeDataProvider')]
     public function testMergeWithSelf(array $initial, array $values, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $this->assertToArray($initial, $instance->merge($instance));
         $this->assertToArray($initial, $instance);
diff --git a/tests/Map/pairs.php b/tests/Map/pairs.php
index 87771f0..584c5d4 100644
--- a/tests/Map/pairs.php
+++ b/tests/Map/pairs.php
@@ -1,11 +1,13 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 use Ds\Vector;
 
 trait pairs
 {
-    public function pairsDataProvider()
+    public static function pairsDataProvider()
     {
         return [
             [[], []],
@@ -13,12 +15,10 @@ public function pairsDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider pairsDataProvider
-     */
+    #[DataProvider('pairsDataProvider')]
     public function testPairs(array $initial, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $pairs = $instance->pairs();
 
         $this->assertInstanceOf(Vector::class, $pairs);
@@ -35,7 +35,7 @@ public function testObjectsAreMutableThroughAccess()
         $key = new \stdClass();
         $key->state = true;
 
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->put($key, 1);
 
         $instance->pairs()->first()->key->state = false;
@@ -46,7 +46,7 @@ public function testObjectsAreMutableThroughAccess()
 
     public function testKeysAreNotMutableThroughAccess()
     {
-        $instance = $this->getInstance(['a' => 1, 'b' => 2]);
+        $instance = static::getInstance(['a' => 1, 'b' => 2]);
         $instance->pairs()->first()->key = 'c';
 
         $this->assertEquals('a', $instance->pairs()->first()->key);
diff --git a/tests/Map/put.php b/tests/Map/put.php
index b6d52d6..bc81875 100644
--- a/tests/Map/put.php
+++ b/tests/Map/put.php
@@ -1,11 +1,13 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 use Ds\Tests\HashableObject;
 
 trait put
 {
-    public function putDataProvider()
+    public static function putDataProvider()
     {
         $o = new \stdClass();
 
@@ -39,7 +41,7 @@ public function putDataProvider()
         ];
     }
 
-    public function putHashableDataProvider()
+    public static function putHashableDataProvider()
     {
         // Two objects with the same hash code and equals.
         $h1 = new HashableObject(1);
@@ -55,12 +57,10 @@ public function putHashableDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider putDataProvider
-     */
+    #[DataProvider('putDataProvider')]
     public function testPut(array $pairs, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($pairs as $pair) {
             $instance->put($pair[0], $pair[1]);
@@ -75,7 +75,7 @@ public function testPut(array $pairs, array $expected)
 
     public function testPutMany()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         for ($i = 0; $i < self::MANY; $i++) {
             $instance->put(rand(), rand());
@@ -85,9 +85,7 @@ public function testPutMany()
         $this->assertEquals(self::MANY, count($instance->toArray()));
     }
 
-    /**
-     * @dataProvider putHashableDataProvider
-     */
+    #[DataProvider('putHashableDataProvider')]
     public function testPutHashable(array $pairs, array $expected)
     {
         $this->testPut($pairs, $expected);
@@ -95,21 +93,21 @@ public function testPutHashable(array $pairs, array $expected)
 
     public function testArrayAccessPut()
     {
-        $instance = $this->getInstance(['a' => 1]);
+        $instance = static::getInstance(['a' => 1]);
         $instance['a'] = 2;
         $this->assertToArray(['a' => 2], $instance);
     }
 
     public function testArrayAccessPutByMethod()
     {
-        $instance = $this->getInstance(['a' => 1]);
+        $instance = static::getInstance(['a' => 1]);
         $instance->offsetSet('a', 2);
         $this->assertToArray(['a' => 2], $instance);
     }
 
     public function testArrayAccessPutByReference()
     {
-        $instance = $this->getInstance(['a' => [1]]);
+        $instance = static::getInstance(['a' => [1]]);
         $instance['a'][0] = 2;
 
         $this->assertToArray(['a' => [2]], $instance);
@@ -117,8 +115,8 @@ public function testArrayAccessPutByReference()
 
     public function testMapPutCircularReference()
     {
-        $a = $this->getInstance();
-        $b = $this->getInstance();
+        $a = static::getInstance();
+        $b = static::getInstance();
 
         $a->put("B", $b);
         $a->put("A", $a);
@@ -131,7 +129,7 @@ public function testMapPutCircularReference()
 
     public function testPutKeyAsReference()
     {
-        $map = $this->getInstance();
+        $map = static::getInstance();
 
         $key = ['a'];
         $ref = &$key;
@@ -159,7 +157,7 @@ public function testPutKeyAsReference()
 
     public function testArrayAccessPutKeyAsReference()
     {
-        $map = $this->getInstance();
+        $map = static::getInstance();
 
         $key = ['a'];
         $ref = &$key;
diff --git a/tests/Map/putAll.php b/tests/Map/putAll.php
index 5eec34d..dfc3e03 100644
--- a/tests/Map/putAll.php
+++ b/tests/Map/putAll.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait putAll
 {
-    public function putAllDataProvider()
+    public static function putAllDataProvider()
     {
         // values, values
         return [
@@ -11,105 +13,87 @@ public function putAllDataProvider()
             [['a']],
             [['a', 'b']],
             [['a', 'b', 'c']],
-            [$this->sample()],
+            [self::sample()],
             [range(1, self::MANY)],
         ];
     }
 
-    /**
-     * @dataProvider putAllDataProvider
-     */
+    #[DataProvider('putAllDataProvider')]
     public function testPutAll(array $values)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->putAll($values);
         $this->assertToArray($values, $instance);
     }
 
-    /**
-     * @dataProvider putAllDataProvider
-     */
+    #[DataProvider('putAllDataProvider')]
     public function testPutAllUsingIterator(array $values)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->putAll(new \ArrayIterator($values));
         $this->assertToArray($values, $instance);
     }
 
-    /**
-     * @dataProvider putAllDataProvider
-     */
+    #[DataProvider('putAllDataProvider')]
     public function testPutAllFromSet(array $values)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $set = new \Ds\Set($values);
         $instance->putAll($set);
         $this->assertToArray($values, $instance);
     }
 
-    /**
-     * @dataProvider putAllDataProvider
-     */
+    #[DataProvider('putAllDataProvider')]
     public function testPutAllFromMap(array $values)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $map = new \Ds\Map($values);
         $instance->putAll($map);
         $this->assertToArray($values, $instance);
     }
 
-    /**
-     * @dataProvider putAllDataProvider
-     */
+    #[DataProvider('putAllDataProvider')]
     public function testPutAllFromVector(array $values)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $vector = new \Ds\Vector($values);
         $instance->putAll($vector);
         $this->assertToArray($values, $instance);
     }
 
-    /**
-     * @dataProvider putAllDataProvider
-     */
+    #[DataProvider('putAllDataProvider')]
     public function testPutAllFromDeque(array $values)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $deque = new \Ds\Deque($values);
         $instance->putAll($deque);
         $this->assertToArray($values, $instance);
     }
 
-    /**
-     * @dataProvider putAllDataProvider
-     */
+    #[DataProvider('putAllDataProvider')]
     public function testPutAllFromStack(array $values)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $stack = new \Ds\Stack(array_reverse($values));
         $instance->putAll($stack);
         $this->assertToArray($values, $instance);
         $this->assertCount(0, $stack);
     }
 
-    /**
-     * @dataProvider putAllDataProvider
-     */
+    #[DataProvider('putAllDataProvider')]
     public function testPutAllFromQueue(array $values)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $queue = new \Ds\Queue($values);
         $instance->putAll($queue);
         $this->assertToArray($values, $instance);
         $this->assertCount(0, $queue);
     }
 
-    /**
-     * @dataProvider putAllDataProvider
-     */
+    #[DataProvider('putAllDataProvider')]
     public function testPutAllFromPriorityQueue(array $values)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $queue = new \Ds\PriorityQueue();
 
         foreach ($values as $value) {
diff --git a/tests/Map/reduce.php b/tests/Map/reduce.php
index 59fad80..e44c55b 100644
--- a/tests/Map/reduce.php
+++ b/tests/Map/reduce.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait reduce
 {
-    public function reduceDataProvider()
+    public static function reduceDataProvider()
     {
         // values, initial, callback, expected
         return [
@@ -34,7 +36,7 @@ function ($c, $k, $v) { return $c * $v; },
         ];
     }
 
-    public function reduceWithoutInitialDataProvider()
+    public static function reduceWithoutInitialDataProvider()
     {
         // values, callback, expected
         return [
@@ -62,12 +64,10 @@ function ($c, $k, $v) { return $c * $v; },
         ];
     }
 
-    /**
-     * @dataProvider reduceDataProvider
-     */
+    #[DataProvider('reduceDataProvider')]
     public function testReduce(array $values, $initial, callable $callback, $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $reduced = $instance->reduce($callback, $initial);
 
@@ -75,12 +75,10 @@ public function testReduce(array $values, $initial, callable $callback, $expecte
         $this->assertEquals($expected, $reduced);
     }
 
-    /**
-     * @dataProvider reduceWithoutInitialDataProvider
-     */
+    #[DataProvider('reduceWithoutInitialDataProvider')]
     public function testReduceWithoutInitial(array $values, callable $callback, $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $reduced = $instance->reduce($callback);
 
@@ -90,7 +88,7 @@ public function testReduceWithoutInitial(array $values, callable $callback, $exp
 
     public function testReduceCallbackThrowsException()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $result = null;
 
         try {
@@ -108,7 +106,7 @@ public function testReduceCallbackThrowsException()
 
     public function testReduceCallbackThrowsExceptionLaterOn()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $result = null;
 
         try {
diff --git a/tests/Map/remove.php b/tests/Map/remove.php
index 303be6c..eb71a34 100644
--- a/tests/Map/remove.php
+++ b/tests/Map/remove.php
@@ -1,11 +1,13 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 use Ds\Tests\HashableObject;
 
 trait remove
 {
-    public function removeDataProvider()
+    public static function removeDataProvider()
     {
         $o = new \stdClass();
 
@@ -23,7 +25,7 @@ public function removeDataProvider()
         ];
     }
 
-    public function removeHashableDataProvider()
+    public static function removeHashableDataProvider()
     {
         // Two objects with the same hash code and equals.
         $h1 = new HashableObject(1);
@@ -35,9 +37,7 @@ public function removeHashableDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider removeHashableDataProvider
-     */
+    #[DataProvider('removeHashableDataProvider')]
     public function testRemoveHashable(array $initial, $key, $expected, array $result)
     {
         $this->testRemove($initial, $key, $expected, $result);
@@ -45,7 +45,7 @@ public function testRemoveHashable(array $initial, $key, $expected, array $resul
 
     public function testRemoveAllFromFront()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         for ($i = 0; $i < self::MANY; $i++) {
             $instance->put($i, $i);
@@ -62,7 +62,7 @@ public function testRemoveAllFromFront()
 
     public function testRemoveHalfFromMidway()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $size = self::MANY + (self::MANY & 1); // Force even
         $half = intdiv($size, 2);
@@ -80,7 +80,7 @@ public function testRemoveHalfFromMidway()
 
     public function testRandomRemove()
     {
-        $instance  = $this->getInstance();
+        $instance  = static::getInstance();
         $reference = [];
 
         for ($i = 0; $i < 10; $i++) {
@@ -105,12 +105,10 @@ public function testRandomRemove()
         $this->assertToArray($reference, $instance);
     }
 
-    /**
-     * @dataProvider removeDataProvider
-     */
+    #[DataProvider('removeDataProvider')]
     public function testRemove(array $initial, $key, $expected, array $result)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($initial as $pair) {
             $instance->put($pair[0], $pair[1]);
@@ -122,13 +120,13 @@ public function testRemove(array $initial, $key, $expected, array $result)
 
     public function testRemoveDefault()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertEquals('a', $instance->remove('?', 'a'));
     }
 
     public function testRemoveKeyNotFound()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectKeyNotFoundException();
         $instance->remove('?');
     }
diff --git a/tests/Map/reverse.php b/tests/Map/reverse.php
index 92204cf..c850f6c 100644
--- a/tests/Map/reverse.php
+++ b/tests/Map/reverse.php
@@ -1,23 +1,23 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait reverse
 {
-    public function reverseDataProvider()
+    public static function reverseDataProvider()
     {
         $reverse = function($a) {
             return [$a[0], array_reverse($a[1], 1)];
         };
 
-        return array_map($reverse, $this->basicDataProvider());
+        return array_map($reverse, self::basicDataProvider());
     }
 
-    /**
-     * @dataProvider reverseDataProvider
-     */
+    #[DataProvider('reverseDataProvider')]
     public function testReverse(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $instance->reverse();
 
         $this->assertToArray($expected, $instance);
diff --git a/tests/Map/reversed.php b/tests/Map/reversed.php
index e90e4d8..e469e9b 100644
--- a/tests/Map/reversed.php
+++ b/tests/Map/reversed.php
@@ -1,23 +1,23 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait reversed
 {
-    public function reversedDataProvider()
+    public static function reversedDataProvider()
     {
         $reverse = function($a) {
             return [$a[0], array_reverse($a[1], 1)];
         };
 
-        return array_map($reverse, $this->basicDataProvider());
+        return array_map($reverse, self::basicDataProvider());
     }
 
-    /**
-     * @dataProvider reversedDataProvider
-     */
+    #[DataProvider('reversedDataProvider')]
     public function testReversed(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertToArray($expected, $instance->reversed());
     }
 }
diff --git a/tests/Map/skip.php b/tests/Map/skip.php
index f015ec4..55bcb61 100644
--- a/tests/Map/skip.php
+++ b/tests/Map/skip.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait skip
 {
-    public function skipDataProvider()
+    public static function skipDataProvider()
     {
         // values, position, returned pair
         return [
@@ -16,7 +18,7 @@ public function skipDataProvider()
         ];
     }
 
-    public function skipOutOfRangeDataProvider()
+    public static function skipOutOfRangeDataProvider()
     {
         return [
             [[   ], -1],
@@ -27,24 +29,20 @@ public function skipOutOfRangeDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider skipDataProvider
-     */
+    #[DataProvider('skipDataProvider')]
     public function testSkip(array $values, int $position, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $pair = $instance->skip($position);
 
         $this->assertEquals($expected, [$pair->key, $pair->value]);
     }
 
-    /**
-     * @dataProvider skipOutOfRangeDataProvider
-     */
+    #[DataProvider('skipOutOfRangeDataProvider')]
     public function testSkipIndexOutOfRange(array $values, int $position)
     {
         $this->expectIndexOutOfRangeException();
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $instance->skip($position);
     }
 }
diff --git a/tests/Map/slice.php b/tests/Map/slice.php
index 149e767..b36e5ba 100644
--- a/tests/Map/slice.php
+++ b/tests/Map/slice.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait slice
 {
-    public function sliceDataProvider()
+    public static function sliceDataProvider()
     {
         $a = ['a', 'b', 'c'];
         $n = count($a);
@@ -20,12 +22,10 @@ public function sliceDataProvider()
         return $data;
     }
 
-    /**
-     * @dataProvider sliceDataProvider
-     */
+    #[DataProvider('sliceDataProvider')]
     public function testSlice(array $values, int $index, int $length)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $sliced = $instance->slice($index, $length);
         $expected = array_slice($values, $index, $length, true);
@@ -34,12 +34,10 @@ public function testSlice(array $values, int $index, int $length)
         $this->assertToArray($expected, $sliced);
     }
 
-    /**
-     * @dataProvider sliceDataProvider
-     */
+    #[DataProvider('sliceDataProvider')]
     public function testSliceWithoutLength(array $values, int $index, int $length)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $sliced = $instance->slice($index);
         $expected = array_slice($values, $index, null, true);
@@ -48,12 +46,10 @@ public function testSliceWithoutLength(array $values, int $index, int $length)
         $this->assertToArray($expected, $sliced);
     }
 
-    /**
-     * @dataProvider sliceDataProvider
-     */
+    #[DataProvider('sliceDataProvider')]
     public function testSliceWithLengthNull(array $values, int $index, int $length)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $sliced = $instance->slice($index, null);
         $expected = array_slice($values, $index, null, true);
@@ -64,7 +60,7 @@ public function testSliceWithLengthNull(array $values, int $index, int $length)
 
     public function testSliceAfterRemoveOutsideOfSlice()
     {
-        $instance = $this->getInstance(['a', 'b', 'c', 'd', 'e']);
+        $instance = static::getInstance(['a', 'b', 'c', 'd', 'e']);
         $instance->remove(3); // d
 
         $this->assertToArray(['a', 'b', 'c'], $instance->slice(0, 3));
@@ -72,7 +68,7 @@ public function testSliceAfterRemoveOutsideOfSlice()
 
     public function testSliceAfterRemoveAtStartOfSlice()
     {
-        $instance = $this->getInstance(['a', 'b', 'c', 'd', 'e']);
+        $instance = static::getInstance(['a', 'b', 'c', 'd', 'e']);
         $instance->remove(1); // b
 
         $this->assertToArray([
@@ -84,7 +80,7 @@ public function testSliceAfterRemoveAtStartOfSlice()
 
     public function testSliceAfterRemoveWithinSlice()
     {
-        $instance = $this->getInstance(['a', 'b', 'c', 'd', 'e']);
+        $instance = static::getInstance(['a', 'b', 'c', 'd', 'e']);
         $instance->remove(2); // c
 
         $this->assertToArray([
diff --git a/tests/Map/sort.php b/tests/Map/sort.php
index 473459a..67be7b1 100644
--- a/tests/Map/sort.php
+++ b/tests/Map/sort.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait sort
 {
-    public function sortDataProvider()
+    public static function sortDataProvider()
     {
         return [
             [[
@@ -24,12 +26,10 @@ public function sortDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider sortDataProvider
-     */
+    #[DataProvider('sortDataProvider')]
     public function testSort(array $values)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $expected = array_slice($values, 0, count($values), true);
         asort($expected);
@@ -38,12 +38,10 @@ public function testSort(array $values)
         $this->assertToArray($expected, $instance);
     }
 
-    /**
-     * @dataProvider sortDataProvider
-     */
+    #[DataProvider('sortDataProvider')]
     public function testSortUsingComparator(array $values)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $expected = array_slice($values, 0, count($values), true);
         arsort($expected);
diff --git a/tests/Map/sorted.php b/tests/Map/sorted.php
index 671c02b..4391543 100644
--- a/tests/Map/sorted.php
+++ b/tests/Map/sorted.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait sorted
 {
-    public function sortedDataProvider()
+    public static function sortedDataProvider()
     {
         return [
             [[
@@ -24,12 +26,10 @@ public function sortedDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider sortedDataProvider
-     */
+    #[DataProvider('sortedDataProvider')]
     public function testSorted(array $values)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $expected = array_slice($values, 0, count($values), true);
         asort($expected);
@@ -38,12 +38,10 @@ public function testSorted(array $values)
         $this->assertToArray($values, $instance);
     }
 
-    /**
-     * @dataProvider sortedDataProvider
-     */
+    #[DataProvider('sortedDataProvider')]
     public function testSortedUsingComparator(array $values)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $sorted = $instance->sorted(function($a, $b) {
             return $b <=> $a;
diff --git a/tests/Map/sum.php b/tests/Map/sum.php
index fd9e0dc..3125cb9 100644
--- a/tests/Map/sum.php
+++ b/tests/Map/sum.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait sum
 {
-    public function sumDataProvider()
+    public static function sumDataProvider()
     {
         $nonNumbers = version_compare(PHP_VERSION, '8.3.0', '>=') ? [true, false, null] : ["a", true, false, null];
         return [
@@ -28,12 +30,10 @@ public function sumDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider sumDataProvider
-     */
+    #[DataProvider('sumDataProvider')]
     public function testSum($values, $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertEquals($expected, $instance->sum());
     }
 }
diff --git a/tests/Map/toArray.php b/tests/Map/toArray.php
index ea83264..3ac0a4f 100644
--- a/tests/Map/toArray.php
+++ b/tests/Map/toArray.php
@@ -5,7 +5,7 @@ trait toArray
 {
     public function testToArrayWithBadKey()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->put(new \stdClass(), 1);
 
         $this->expectInternalIllegalOffset();
diff --git a/tests/Map/union.php b/tests/Map/union.php
index a382778..28d6418 100644
--- a/tests/Map/union.php
+++ b/tests/Map/union.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait union
 {
-    public function unionDataProvider()
+    public static function unionDataProvider()
     {
         // A, B, expected
         return [
@@ -16,24 +18,20 @@ public function unionDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider unionDataProvider
-     */
+    #[DataProvider('unionDataProvider')]
     public function testUnion(array $initial, array $values, array $expected)
     {
-        $instance = $this->getInstance($initial);
-        $other    = $this->getInstance($values);
+        $instance = static::getInstance($initial);
+        $other    = static::getInstance($values);
 
         $this->assertToArray($expected, $instance->union($other));
         $this->assertToArray($initial, $instance);
     }
 
-    /**
-     * @dataProvider unionDataProvider
-     */
+    #[DataProvider('unionDataProvider')]
     public function testUnionWithSelf(array $initial, array $values, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $this->assertToArray($initial, $instance->union($instance));
         $this->assertToArray($initial, $instance);
diff --git a/tests/Map/values.php b/tests/Map/values.php
index 0afee57..ae7ec18 100644
--- a/tests/Map/values.php
+++ b/tests/Map/values.php
@@ -1,11 +1,13 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 use Ds\Vector;
 
 trait values
 {
-    public function valuesDataProvider()
+    public static function valuesDataProvider()
     {
         return [
 
@@ -17,12 +19,10 @@ public function valuesDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider valuesDataProvider
-     */
+    #[DataProvider('valuesDataProvider')]
     public function testValues(array $initial, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $values = $instance->values();
 
         $this->assertInstanceOf(Vector::class, $values);
diff --git a/tests/Map/xor_.php b/tests/Map/xor_.php
index 6f79e10..6a88865 100644
--- a/tests/Map/xor_.php
+++ b/tests/Map/xor_.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Map;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait xor_
 {
-    public function xorDataProvider()
+    public static function xorDataProvider()
     {
         // Keys in either A or B, but not both.
         // A, B, expected result
@@ -17,23 +19,19 @@ public function xorDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider xorDataProvider
-     */
+    #[DataProvider('xorDataProvider')]
     public function testXor(array $a, array $b, array $expected)
     {
-        $a = $this->getInstance($a);
-        $b = $this->getInstance($b);
+        $a = static::getInstance($a);
+        $b = static::getInstance($b);
 
         $this->assertEquals($expected, $a->xor($b)->toArray());
     }
 
-    /**
-     * @dataProvider xorDataProvider
-     */
+    #[DataProvider('xorDataProvider')]
     public function testXorWithSelf(array $a, array $b, array $expected)
     {
-        $map = $this->getInstance($a);
+        $map = static::getInstance($a);
 
         $this->assertEquals([], $map->xor($map)->toArray());
     }
diff --git a/tests/MapTest.php b/tests/MapTest.php
index af075e6..1a0900e 100644
--- a/tests/MapTest.php
+++ b/tests/MapTest.php
@@ -4,7 +4,7 @@
 use ArrayAccess;
 use Ds\Vector;
 
-class MapTest extends CollectionTest
+class MapTest extends CollectionTestCase
 {
     use Map\__construct;
     use Map\_clone;
@@ -54,14 +54,14 @@ class MapTest extends CollectionTest
     use Map\values;
     use Map\xor_;
 
-    public function getInstance(array $values = [])
+    public static function getInstance(array $values = [])
     {
         return new \Ds\Map($values);
     }
 
     public function testCollisionChain()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         // We want to add three distinct values with the same hash mod.
         $instance->put( 3, 'a');
@@ -75,7 +75,7 @@ public function testCollisionChain()
 
     public function testCollisionChainAcrossResize()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $n = 64;
 
@@ -90,7 +90,7 @@ public function testCollisionChainAcrossResize()
 
     public function testNonPackedRehash()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->put( 3, 'a');
         $instance->put(11, 'b');
@@ -114,7 +114,7 @@ public function testNonPackedRehash()
 
     public function testPutAfterRemove()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->put(1, 1);
         $instance->put(2, 2);
 
@@ -126,7 +126,7 @@ public function testPutAfterRemove()
 
     public function testRandomPutAndRemove()
     {
-        $instance  = $this->getInstance();
+        $instance  = static::getInstance();
         $reference = [];
 
         for ($i = 0; $i < self::MANY; $i++) {
@@ -151,7 +151,7 @@ public function testRandomPutAndRemove()
 
     public function testAlternatingPutAndRemove()
     {
-        $instance  = $this->getInstance();
+        $instance  = static::getInstance();
         $reference = [];
 
         for ($i = 0; $i < self::MANY; $i++) {
@@ -174,7 +174,7 @@ public function testAlternatingPutAndRemove()
 
     public function testImplementsArrayAccess()
     {
-        $this->assertInstanceOf(ArrayAccess::class, $this->getInstance());
+        $this->assertInstanceOf(ArrayAccess::class, static::getInstance());
     }
 
     /**
@@ -183,8 +183,8 @@ public function testImplementsArrayAccess()
     public function testIssue200()
     {
         static::expectNotToPerformAssertions();
-        $map = $this->getInstance();
-        $map->put('#200', $this->getInstance());
+        $map = static::getInstance();
+        $map->put('#200', static::getInstance());
         $map->keys()->merge($map->keys());
     }
 }
diff --git a/tests/PairTest.php b/tests/PairTest.php
index edf8732..acfb7fe 100644
--- a/tests/PairTest.php
+++ b/tests/PairTest.php
@@ -1,7 +1,7 @@
 <?php
 namespace Ds\Tests;
 
-class PairTest extends CollectionTest
+class PairTest extends CollectionTestCase
 {
     use Pair\__construct;
     use Pair\__get;
@@ -18,6 +18,11 @@ class PairTest extends CollectionTest
     use Pair\copy;
     use Pair\toArray;
 
+    public static function getInstance(array $values = [])
+    {
+        return new \Ds\Pair($values[0] ?? null, $values[1] ?? null);
+    }
+
     private function getPair($key, $value)
     {
         return new \Ds\Pair($key, $value);
diff --git a/tests/PriorityQueue/_clone.php b/tests/PriorityQueue/_clone.php
index fd1e099..7f71d88 100644
--- a/tests/PriorityQueue/_clone.php
+++ b/tests/PriorityQueue/_clone.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\PriorityQueue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _clone
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testClone($values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $clone = clone $instance;
 
diff --git a/tests/PriorityQueue/_echo.php b/tests/PriorityQueue/_echo.php
index 379b595..70063de 100644
--- a/tests/PriorityQueue/_echo.php
+++ b/tests/PriorityQueue/_echo.php
@@ -5,6 +5,6 @@ trait _echo
 {
     public function testEcho()
     {
-        $this->assertInstanceToString($this->getInstance());
+        $this->assertInstanceToString(static::getInstance());
     }
 }
diff --git a/tests/PriorityQueue/_empty.php b/tests/PriorityQueue/_empty.php
index 1e9045c..ef3c88e 100644
--- a/tests/PriorityQueue/_empty.php
+++ b/tests/PriorityQueue/_empty.php
@@ -5,7 +5,7 @@ trait _empty
 {
     public function testArrayAccessEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         empty($instance['?']);
     }
diff --git a/tests/PriorityQueue/_foreach.php b/tests/PriorityQueue/_foreach.php
index 35e4b71..18d8b87 100644
--- a/tests/PriorityQueue/_foreach.php
+++ b/tests/PriorityQueue/_foreach.php
@@ -5,7 +5,7 @@ trait _foreach
 {
     public function testForEach()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->push('a', 1);
         $instance->push('c', 3);
diff --git a/tests/PriorityQueue/_isset.php b/tests/PriorityQueue/_isset.php
index 5e2e266..9099a2f 100644
--- a/tests/PriorityQueue/_isset.php
+++ b/tests/PriorityQueue/_isset.php
@@ -5,7 +5,7 @@ trait _isset
 {
     public function testArrayAccessIsset()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         isset($instance['?']);
     }
diff --git a/tests/PriorityQueue/_jsonEncode.php b/tests/PriorityQueue/_jsonEncode.php
index 6ddbae6..da79639 100644
--- a/tests/PriorityQueue/_jsonEncode.php
+++ b/tests/PriorityQueue/_jsonEncode.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\PriorityQueue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _jsonEncode
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testJsonEncode(array $initial, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals(json_encode($expected), json_encode($instance));
     }
 }
diff --git a/tests/PriorityQueue/_serialize.php b/tests/PriorityQueue/_serialize.php
index 4a1cdb1..9b5e098 100644
--- a/tests/PriorityQueue/_serialize.php
+++ b/tests/PriorityQueue/_serialize.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\PriorityQueue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _serialize
 {
-    public function serializeDataProvider()
+    public static function serializeDataProvider()
     {
         return [
             [
@@ -12,12 +14,10 @@ public function serializeDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider serializeDataProvider
-     */
+    #[DataProvider('serializeDataProvider')]
     public function testSerialize(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertSerialized($expected, $instance, true);
     }
 }
diff --git a/tests/PriorityQueue/_unset.php b/tests/PriorityQueue/_unset.php
index afbd8a7..defe43f 100644
--- a/tests/PriorityQueue/_unset.php
+++ b/tests/PriorityQueue/_unset.php
@@ -5,7 +5,7 @@ trait _unset
 {
     public function testArrayAccessUnset()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         unset($instance['?']);
     }
diff --git a/tests/PriorityQueue/_var_dump.php b/tests/PriorityQueue/_var_dump.php
index 02d2373..0714b19 100644
--- a/tests/PriorityQueue/_var_dump.php
+++ b/tests/PriorityQueue/_var_dump.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\PriorityQueue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _var_dump
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testVarDump(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertInstanceDump($expected, $instance);
     }
 }
diff --git a/tests/PriorityQueue/allocate.php b/tests/PriorityQueue/allocate.php
index c478ea1..187d503 100644
--- a/tests/PriorityQueue/allocate.php
+++ b/tests/PriorityQueue/allocate.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\PriorityQueue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait allocate
 {
-    public function allocateDataProvider()
+    public static function allocateDataProvider()
     {
         // initial, allocation, expected capacity
         return [
@@ -20,12 +22,10 @@ public function allocateDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider allocateDataProvider
-     */
+    #[DataProvider('allocateDataProvider')]
     public function testAllocate(int $initial, int $allocate, int $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->allocate($initial);
         $instance->allocate($allocate);
diff --git a/tests/PriorityQueue/capacity.php b/tests/PriorityQueue/capacity.php
index 2dfdefe..cf3aec4 100644
--- a/tests/PriorityQueue/capacity.php
+++ b/tests/PriorityQueue/capacity.php
@@ -9,7 +9,7 @@ public function testCapacity()
     {
         $min = PriorityQueue::MIN_CAPACITY;
 
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertEquals($min, $instance->capacity());
 
         for ($i = 0; $i < $min; $i++) {
@@ -44,7 +44,7 @@ public function testAutoTruncate()
             0  =>  8,
         ];
 
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach (range(1, array_keys($boundaries)[0]) as $value) {
             $instance->push($value, 1);
@@ -65,7 +65,7 @@ public function testAutoTruncate()
 
     public function testClearResetsCapacity()
     {
-        $instance = $this->getInstance(range(1, self::MANY));
+        $instance = static::getInstance(range(1, self::MANY));
         $instance->clear();
         $this->assertEquals(PriorityQueue::MIN_CAPACITY, $instance->capacity());
     }
diff --git a/tests/PriorityQueue/clear.php b/tests/PriorityQueue/clear.php
index 1438807..6c104c3 100644
--- a/tests/PriorityQueue/clear.php
+++ b/tests/PriorityQueue/clear.php
@@ -5,7 +5,7 @@ trait clear
 {
     public function testClear()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach (range(1, self::MANY) as $i) {
             $instance->push($i, rand());
diff --git a/tests/PriorityQueue/copy.php b/tests/PriorityQueue/copy.php
index e66047c..8055763 100644
--- a/tests/PriorityQueue/copy.php
+++ b/tests/PriorityQueue/copy.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\PriorityQueue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait copy
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testCopy(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $copy = $instance->copy();
 
         $this->assertEquals($instance->toArray(), $copy->toArray());
@@ -17,7 +17,7 @@ public function testCopy(array $values, array $expected)
 
     public function testCopyDoesNotAffectSubject()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->push('a', 1);
         $instance->push('b', 2);
         $instance->push('c', 3);
diff --git a/tests/PriorityQueue/count.php b/tests/PriorityQueue/count.php
index 9027ee0..5620288 100644
--- a/tests/PriorityQueue/count.php
+++ b/tests/PriorityQueue/count.php
@@ -5,7 +5,7 @@ trait count
 {
     public function testCount()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach (range(1, self::MANY) as $i) {
             $instance->push($i, rand());
diff --git a/tests/PriorityQueue/isEmpty.php b/tests/PriorityQueue/isEmpty.php
index 3c51f5e..b380823 100644
--- a/tests/PriorityQueue/isEmpty.php
+++ b/tests/PriorityQueue/isEmpty.php
@@ -5,7 +5,7 @@ trait isEmpty
 {
     public function testIsEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertTrue($instance->isEmpty());
 
         $instance->push('a', 1);
diff --git a/tests/PriorityQueue/peek.php b/tests/PriorityQueue/peek.php
index e7ce32a..5711dcf 100644
--- a/tests/PriorityQueue/peek.php
+++ b/tests/PriorityQueue/peek.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\PriorityQueue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait peek
 {
-    public function peekDataProvider()
+    public static function peekDataProvider()
     {
         // initial, expected
         return [
@@ -13,19 +15,17 @@ public function peekDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider peekDataProvider
-     */
+    #[DataProvider('peekDataProvider')]
     public function testPeek(array $initial, $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($expected, $instance->peek());
         $this->assertCount(count($initial), $instance);
     }
 
     public function testPeekNotAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->peek();
     }
diff --git a/tests/PriorityQueue/pop.php b/tests/PriorityQueue/pop.php
index b819afc..9c26184 100644
--- a/tests/PriorityQueue/pop.php
+++ b/tests/PriorityQueue/pop.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\PriorityQueue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait pop
 {
-    public function popDataProvider()
+    public static function popDataProvider()
     {
         // initial, expected, result
         return [
@@ -13,12 +15,10 @@ public function popDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider popDataProvider
-     */
+    #[DataProvider('popDataProvider')]
     public function testPop(array $initial, $expected, array $result)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $this->assertEquals($expected, $instance->pop());
         $this->assertToArray($result, $instance);
@@ -26,7 +26,7 @@ public function testPop(array $initial, $expected, array $result)
 
     public function testPopAll()
     {
-        $instance = $this->getInstance(range(1, self::MANY));
+        $instance = static::getInstance(range(1, self::MANY));
 
         while ( ! $instance->isEmpty()) {
             $instance->pop();
@@ -37,7 +37,7 @@ public function testPopAll()
 
     public function testPopNowAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->pop();
     }
diff --git a/tests/PriorityQueue/push.php b/tests/PriorityQueue/push.php
index 32c8826..2e32638 100644
--- a/tests/PriorityQueue/push.php
+++ b/tests/PriorityQueue/push.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\PriorityQueue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait push
 {
-    public function pushDataProvider()
+    public static function pushDataProvider()
     {
         // initial, values, expected
         return [
@@ -18,12 +20,10 @@ public function pushDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testPush(array $initial, array $values, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         foreach ($values as $value => $priority) {
             $instance->push($value, (int) $priority);
@@ -34,7 +34,7 @@ public function testPush(array $initial, array $values, array $expected)
 
     public function testPushIdenticalValues()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->push('a', 1);
         $instance->push('a', 1);
@@ -45,7 +45,7 @@ public function testPushIdenticalValues()
 
     public function testPushManyRandom()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $reference = range(1, self::SOME);
         shuffle($reference);
@@ -61,7 +61,7 @@ public function testPushManyRandom()
 
     public function testInsertionOrder()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach (range(1, self::MANY) as $i) {
             $instance->push($i, 0);
@@ -74,7 +74,7 @@ public function testInsertionOrder()
 
     public function testPushCircularReference()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->push($instance, 1);
         $this->assertToArray([$instance], $instance);
     }
diff --git a/tests/PriorityQueue/toArray.php b/tests/PriorityQueue/toArray.php
index 2c90946..bd55cb2 100644
--- a/tests/PriorityQueue/toArray.php
+++ b/tests/PriorityQueue/toArray.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\PriorityQueue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait toArray
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testToArray(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         // Also check that toArray is not destructive
         $this->assertToArray($expected, $instance);
diff --git a/tests/PriorityQueueTest.php b/tests/PriorityQueueTest.php
index 95bea4d..a8a290b 100644
--- a/tests/PriorityQueueTest.php
+++ b/tests/PriorityQueueTest.php
@@ -1,7 +1,7 @@
 <?php
 namespace Ds\Tests;
 
-class PriorityQueueTest extends CollectionTest
+class PriorityQueueTest extends CollectionTestCase
 {
    use PriorityQueue\__construct;
    use PriorityQueue\_clone;
@@ -26,7 +26,7 @@ class PriorityQueueTest extends CollectionTest
    use PriorityQueue\push;
    use PriorityQueue\toArray;
 
-    public function getInstance(array $values = [])
+    public static function getInstance(array $values = [])
     {
         $queue = new \Ds\PriorityQueue();
 
@@ -37,7 +37,7 @@ public function getInstance(array $values = [])
         return $queue;
     }
 
-    public function basicDataProvider()
+    public static function basicDataProvider()
     {
         return [
             [[], []],
diff --git a/tests/Queue/__construct.php b/tests/Queue/__construct.php
index a543922..931a139 100644
--- a/tests/Queue/__construct.php
+++ b/tests/Queue/__construct.php
@@ -1,32 +1,30 @@
 <?php
 namespace Ds\Tests\Queue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 use Ds\Queue;
 
 trait __construct
 {
-    public function constructDataProvider()
+    public static function constructDataProvider()
     {
         return [
             [[]],
             [['a']],
             [['a', 'a']],
             [['a', 'b']],
-            [$this->sample()],
+            [self::sample()],
         ];
     }
 
-    /**
-     * @dataProvider constructDataProvider
-     */
+    #[DataProvider('constructDataProvider')]
     public function testConstruct(array $values)
     {
         $this->assertToArray($values, new Queue($values));
     }
 
-    /**
-     * @dataProvider constructDataProvider
-     */
+    #[DataProvider('constructDataProvider')]
     public function testConstructUsingIterable(array $values)
     {
         $this->assertToArray($values, new Queue(new \ArrayIterator($values)));
diff --git a/tests/Queue/_clone.php b/tests/Queue/_clone.php
index 60ff7c6..5b8fb5a 100644
--- a/tests/Queue/_clone.php
+++ b/tests/Queue/_clone.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Queue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _clone
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testClone($values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $clone = clone $instance;
 
diff --git a/tests/Queue/_echo.php b/tests/Queue/_echo.php
index d85c112..a1ffb3e 100644
--- a/tests/Queue/_echo.php
+++ b/tests/Queue/_echo.php
@@ -5,6 +5,6 @@ trait _echo
 {
     public function testEcho()
     {
-        $this->assertInstanceToString($this->getInstance());
+        $this->assertInstanceToString(static::getInstance());
     }
 }
diff --git a/tests/Queue/_empty.php b/tests/Queue/_empty.php
index 177874f..a05987f 100644
--- a/tests/Queue/_empty.php
+++ b/tests/Queue/_empty.php
@@ -5,7 +5,7 @@ trait _empty
 {
     public function testArrayAccessEmpty()
     {
-        $set = $this->getInstance();
+        $set = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         empty($set['a']);
     }
diff --git a/tests/Queue/_foreach.php b/tests/Queue/_foreach.php
index 79da3d9..e0cf757 100644
--- a/tests/Queue/_foreach.php
+++ b/tests/Queue/_foreach.php
@@ -5,7 +5,7 @@ trait _foreach
 {
     public function testForEach()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->push('a');
         $instance->push('b');
diff --git a/tests/Queue/_isset.php b/tests/Queue/_isset.php
index 18b265f..94484b6 100644
--- a/tests/Queue/_isset.php
+++ b/tests/Queue/_isset.php
@@ -5,14 +5,14 @@ trait _isset
 {
     public function testArrayAccessIsset()
     {
-        $set = $this->getInstance();
+        $set = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         isset($set['a']);
     }
 
     public function testArrayAccessIssetByMethod()
     {
-        $set = $this->getInstance();
+        $set = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         $set->offsetExists('a');
     }
diff --git a/tests/Queue/_jsonEncode.php b/tests/Queue/_jsonEncode.php
index efc6a1a..ef2f695 100644
--- a/tests/Queue/_jsonEncode.php
+++ b/tests/Queue/_jsonEncode.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Queue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _jsonEncode
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testJsonEncode(array $initial, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals(json_encode($expected), json_encode($instance));
     }
 }
diff --git a/tests/Queue/_list.php b/tests/Queue/_list.php
index 49ab1b3..575a5fb 100644
--- a/tests/Queue/_list.php
+++ b/tests/Queue/_list.php
@@ -5,14 +5,14 @@ trait _list
 {
     public function testList()
     {
-        $instance = $this->getInstance(['a', 'b', 'c']);
+        $instance = static::getInstance(['a', 'b', 'c']);
         $this->expectListNotSupportedException();
         list($a, $b, $c) = $instance;
     }
 
     public function testListByMethod()
     {
-        $instance = $this->getInstance(['a', 'b', 'c']);
+        $instance = static::getInstance(['a', 'b', 'c']);
         $this->expectListNotSupportedException();
         $instance->offsetGet(0);
     }
diff --git a/tests/Queue/_serialize.php b/tests/Queue/_serialize.php
index e4cda85..c96e4cf 100644
--- a/tests/Queue/_serialize.php
+++ b/tests/Queue/_serialize.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Queue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _serialize
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testSerialize(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertSerialized($expected, $instance, false);
     }
 }
diff --git a/tests/Queue/_unset.php b/tests/Queue/_unset.php
index 907bb6b..fe984ce 100644
--- a/tests/Queue/_unset.php
+++ b/tests/Queue/_unset.php
@@ -5,14 +5,14 @@ trait _unset
 {
     public function testArrayAccessUnset()
     {
-        $set = $this->getInstance();
+        $set = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         unset($set['a']);
     }
 
     public function testArrayAccessUnsetByMethod()
     {
-        $set = $this->getInstance();
+        $set = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         $set->offsetUnset('a');
     }
diff --git a/tests/Queue/_var_dump.php b/tests/Queue/_var_dump.php
index 6ceabbf..9a13fee 100644
--- a/tests/Queue/_var_dump.php
+++ b/tests/Queue/_var_dump.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Queue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _var_dump
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testVarDump(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertInstanceDump($expected, $instance);
     }
 }
diff --git a/tests/Queue/clear.php b/tests/Queue/clear.php
index e851efa..614f747 100644
--- a/tests/Queue/clear.php
+++ b/tests/Queue/clear.php
@@ -5,7 +5,7 @@ trait clear
 {
     public function testClear()
     {
-        $instance = $this->getInstance($this->sample());
+        $instance = static::getInstance(self::sample());
         $instance->clear();
 
         $this->assertToArray([], $instance);
diff --git a/tests/Queue/copy.php b/tests/Queue/copy.php
index d9abd7f..f41a57f 100644
--- a/tests/Queue/copy.php
+++ b/tests/Queue/copy.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Queue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait copy
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testCopy(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $copy = $instance->copy();
 
         $this->assertEquals($instance->toArray(), $copy->toArray());
diff --git a/tests/Queue/count.php b/tests/Queue/count.php
index e986b81..79cc69c 100644
--- a/tests/Queue/count.php
+++ b/tests/Queue/count.php
@@ -1,20 +1,20 @@
 <?php
 namespace Ds\Tests\Queue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait count
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testCount(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertCount(count($expected), $instance);
     }
 
     public function testCountEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertCount(0, $instance);
     }
 }
diff --git a/tests/Queue/isEmpty.php b/tests/Queue/isEmpty.php
index eb7339a..b3d2c4f 100644
--- a/tests/Queue/isEmpty.php
+++ b/tests/Queue/isEmpty.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Queue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait isEmpty
 {
-    public function isEmptyDataProvider()
+    public static function isEmptyDataProvider()
     {
         // values, is empty
         return [
@@ -12,18 +14,16 @@ public function isEmptyDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider isEmptyDataProvider
-     */
+    #[DataProvider('isEmptyDataProvider')]
     public function testIsEmpty(array $values, bool $isEmpty)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertEquals($isEmpty, $instance->isEmpty());
     }
 
     public function testIsNotEmptyAfterPop()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertTrue($instance->isEmpty());
 
         $instance->push('a');
diff --git a/tests/Queue/peek.php b/tests/Queue/peek.php
index 0e6e7df..5de4b31 100644
--- a/tests/Queue/peek.php
+++ b/tests/Queue/peek.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Queue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait peek
 {
-    public function peekDataProvider()
+    public static function peekDataProvider()
     {
         // initial, returned, expected result
         return [
@@ -12,12 +14,10 @@ public function peekDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider peekDataProvider
-     */
+    #[DataProvider('peekDataProvider')]
     public function testPeek($initial, $returned)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $value = $instance->peek();
 
@@ -27,7 +27,7 @@ public function testPeek($initial, $returned)
 
     public function testPeekNotAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->peek();
     }
diff --git a/tests/Queue/pop.php b/tests/Queue/pop.php
index 7d38a8d..2590e65 100644
--- a/tests/Queue/pop.php
+++ b/tests/Queue/pop.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Queue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait pop
 {
-    public function popDataProvider()
+    public static function popDataProvider()
     {
         // initial, returned, expected result
         return [
@@ -12,12 +14,10 @@ public function popDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider popDataProvider
-     */
+    #[DataProvider('popDataProvider')]
     public function testPop($initial, $returned, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $value = $instance->pop();
 
@@ -28,14 +28,14 @@ public function testPop($initial, $returned, array $expected)
 
     public function testPopNotAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->pop();
     }
 
     public function testPopAll()
     {
-        $instance = $this->getInstance(range(1, self::MANY));
+        $instance = static::getInstance(range(1, self::MANY));
 
         while ( ! $instance->isEmpty()) {
             $instance->pop();
diff --git a/tests/Queue/push.php b/tests/Queue/push.php
index fcc49d4..2cb029c 100644
--- a/tests/Queue/push.php
+++ b/tests/Queue/push.php
@@ -1,19 +1,19 @@
 <?php
 namespace Ds\Tests\Queue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait push
 {
-    public function pushDataProvider()
+    public static function pushDataProvider()
     {
-        return $this->basicDataProvider();
+        return self::basicDataProvider();
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testPushVariadic(array $values, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->push(...$values);
 
@@ -21,12 +21,10 @@ public function testPushVariadic(array $values, array $expected)
         $this->assertCount(count($expected), $instance);
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testPush(array $values, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($values as $value) {
             $instance->push($value);
@@ -36,12 +34,10 @@ public function testPush(array $values, array $expected)
         $this->assertCount(count($expected), $instance);
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testArrayAccessPush(array $values, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($values as $value) {
             $instance[] = $value;
@@ -51,12 +47,10 @@ public function testArrayAccessPush(array $values, array $expected)
         $this->assertCount(count($expected), $instance);
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testArrayAccessPushByMethod(array $values, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($values as $value) {
             $instance->offsetSet(null, $value);
@@ -68,7 +62,7 @@ public function testArrayAccessPushByMethod(array $values, array $expected)
 
     public function testPushCircularReference()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->push($instance);
         $this->assertToArray([$instance], $instance);
     }
diff --git a/tests/Queue/toArray.php b/tests/Queue/toArray.php
index f346a88..a7b866a 100644
--- a/tests/Queue/toArray.php
+++ b/tests/Queue/toArray.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Queue;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait toArray
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testToArray(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertToArray($expected, $instance);
     }
 }
diff --git a/tests/QueueTest.php b/tests/QueueTest.php
index cbf1f36..c2ccfa0 100644
--- a/tests/QueueTest.php
+++ b/tests/QueueTest.php
@@ -4,7 +4,7 @@
 use ArrayAccess;
 use Ds\Collection;
 
-class QueueTest extends CollectionTest
+class QueueTest extends CollectionTestCase
 {
     use Queue\__construct;
     use Queue\_clone;
@@ -30,20 +30,20 @@ class QueueTest extends CollectionTest
     use Queue\push;
     use Queue\toArray;
 
-    public function getInstance(array $values = [])
+    public static function getInstance(array $values = [])
     {
         return new \Ds\Queue($values);
     }
 
     public function testArrayAccessSet()
     {
-        $set = $this->getInstance();
+        $set = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         $set['a'] = 1;
     }
 
     public function testImplementsArrayAccess()
     {
-        $this->assertInstanceOf(ArrayAccess::class, $this->getInstance());
+        $this->assertInstanceOf(ArrayAccess::class, static::getInstance());
     }
 }
diff --git a/tests/Sequence/_clone.php b/tests/Sequence/_clone.php
index e76bdd8..f30ae08 100644
--- a/tests/Sequence/_clone.php
+++ b/tests/Sequence/_clone.php
@@ -1,19 +1,19 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _clone
 {
-    public function cloneDataProvider()
+    public static function cloneDataProvider()
     {
-        return $this->basicDataProvider();
+        return self::basicDataProvider();
     }
 
-    /**
-     * @dataProvider cloneDataProvider
-     */
+    #[DataProvider('cloneDataProvider')]
     public function testClone($values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $clone = clone $instance;
 
diff --git a/tests/Sequence/_echo.php b/tests/Sequence/_echo.php
index 779edcc..c9f5557 100644
--- a/tests/Sequence/_echo.php
+++ b/tests/Sequence/_echo.php
@@ -5,6 +5,6 @@ trait _echo
 {
     public function testEcho()
     {
-        $this->assertInstanceToString($this->getInstance());
+        $this->assertInstanceToString(static::getInstance());
     }
 }
diff --git a/tests/Sequence/_empty.php b/tests/Sequence/_empty.php
index 24634d1..1341b59 100644
--- a/tests/Sequence/_empty.php
+++ b/tests/Sequence/_empty.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _empty
 {
-    public function emptyDataProvider()
+    public static function emptyDataProvider()
     {
         // initial, index, empty
         return [
@@ -36,39 +38,31 @@ public function emptyDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider emptyDataProvider
-     */
+    #[DataProvider('emptyDataProvider')]
     public function testArrayAccessEmpty($initial, $index, bool $empty)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($empty, empty($instance[$index]));
     }
 
-    /**
-     * @dataProvider badIndexDataProvider
-     */
+    #[DataProvider('badIndexDataProvider')]
     public function testArrayAccessEmptyIndexBadIndex($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertTrue(empty($instance[$index]));
     }
 
-    /**
-     * @dataProvider outOfRangeDataProvider
-     */
+    #[DataProvider('outOfRangeDataProvider')]
     public function testArrayAccessEmptyIndexOutOfRange($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertTrue(empty($instance[$index]));
     }
 
-    /**
-     * @dataProvider emptyDataProvider
-     */
+    #[DataProvider('emptyDataProvider')]
     public function testArrayAccessEmptyByReference($initial, $index, bool $empty)
     {
-        $instance = $this->getInstance([$initial]);
+        $instance = static::getInstance([$initial]);
         $this->assertEquals($empty, empty($instance[0][$index]));
     }
 }
diff --git a/tests/Sequence/_foreach.php b/tests/Sequence/_foreach.php
index 3665ca4..b36a86e 100644
--- a/tests/Sequence/_foreach.php
+++ b/tests/Sequence/_foreach.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _foreach
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testForEach(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertForEach($expected, $instance);
     }
 }
diff --git a/tests/Sequence/_isset.php b/tests/Sequence/_isset.php
index 9d2eb30..dc3e53e 100644
--- a/tests/Sequence/_isset.php
+++ b/tests/Sequence/_isset.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _isset
 {
-    public function issetDataProvider()
+    public static function issetDataProvider()
     {
         // initial, index, isset
         return [
@@ -33,49 +35,39 @@ public function issetDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider issetDataProvider
-     */
+    #[DataProvider('issetDataProvider')]
     public function testArrayAccessIsset($initial, $index, bool $isset)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($isset, isset($instance[$index]));
     }
 
-    /**
-     * @dataProvider issetDataProvider
-     */
+    #[DataProvider('issetDataProvider')]
     public function testArrayAccessIssetByMethod($initial, $index, bool $isset)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($isset, $instance->offsetExists($index));
     }
 
-    /**
-     * @dataProvider badIndexDataProvider
-     */
+    #[DataProvider('badIndexDataProvider')]
     public function testArrayAccessIssetIndexBadIndex($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertFalse(isset($instance[$index]));
     }
 
-    /**
-     * @dataProvider outOfRangeDataProvider
-     */
+    #[DataProvider('outOfRangeDataProvider')]
     public function testArrayAccessIssetIndexOutOfRange($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertFalse(isset($instance[$index]));
     }
 
 
-    /**
-     * @dataProvider issetDataProvider
-     */
+    #[DataProvider('issetDataProvider')]
     public function testArrayAccessIssetByReference($initial, $index, bool $isset)
     {
-        $instance = $this->getInstance([$initial]);
+        $instance = static::getInstance([$initial]);
         $this->assertEquals($isset, isset($instance[0][$index]));
     }
 }
diff --git a/tests/Sequence/_jsonEncode.php b/tests/Sequence/_jsonEncode.php
index 6e1bb8e..6dc3a0d 100644
--- a/tests/Sequence/_jsonEncode.php
+++ b/tests/Sequence/_jsonEncode.php
@@ -1,19 +1,19 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _jsonEncode
 {
-    public function jsonEncodeDataProvider()
+    public static function jsonEncodeDataProvider()
     {
-        return $this->basicDataProvider();
+        return self::basicDataProvider();
     }
 
-    /**
-     * @dataProvider jsonEncodeDataProvider
-     */
+    #[DataProvider('jsonEncodeDataProvider')]
     public function testJsonEncode(array $initial, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals(json_encode($expected), json_encode($instance));
     }
 }
diff --git a/tests/Sequence/_list.php b/tests/Sequence/_list.php
index 40df1a7..e3cbba4 100644
--- a/tests/Sequence/_list.php
+++ b/tests/Sequence/_list.php
@@ -5,7 +5,7 @@ trait _list
 {
     public function testList()
     {
-        $instance = $this->getInstance(['a', 'b', 'c']);
+        $instance = static::getInstance(['a', 'b', 'c']);
         list($a, $b, $c) = $instance;
 
         $this->assertEquals('a', $a);
diff --git a/tests/Sequence/_unset.php b/tests/Sequence/_unset.php
index e6663dc..13c3c62 100644
--- a/tests/Sequence/_unset.php
+++ b/tests/Sequence/_unset.php
@@ -1,47 +1,41 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _unset
 {
-    /**
-     * @dataProvider removeDataProvider
-     */
+    #[DataProvider('removeDataProvider')]
     public function testArrayAccessUnset($initial, $index, $return, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         unset($instance[$index]);
         $this->assertToArray($expected, $instance);
         $this->assertEquals(count($expected), count($instance));
     }
 
-    /**
-     * @dataProvider removeDataProvider
-     */
+    #[DataProvider('removeDataProvider')]
     public function testArrayAccessUnsetByMethod($initial, $index, $return, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $instance->offsetUnset($index);
         $this->assertToArray($expected, $instance);
         $this->assertEquals(count($expected), count($instance));
     }
 
-    /**
-     * @dataProvider badIndexDataProvider
-     */
+    #[DataProvider('badIndexDataProvider')]
     public function testArrayAccessUnsetIndexBadIndex($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         unset($instance[$index]);
         
         $this->assertFalse(isset($instance[$index]));
     }
 
-    /**
-     * @dataProvider outOfRangeDataProvider
-     */
+    #[DataProvider('outOfRangeDataProvider')]
     public function testArrayAccessUnsetIndexOutOfRange($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         unset($instance[$index]);
         
         $this->assertFalse(isset($instance[$index]));
@@ -50,7 +44,7 @@ public function testArrayAccessUnsetIndexOutOfRange($initial, $index)
 
     public function testArrayAccessUnsetByReference()
     {
-        $instance = $this->getInstance([[1]]);
+        $instance = static::getInstance([[1]]);
         unset($instance[0][0]);
 
         $this->assertToArray([[]], $instance);
diff --git a/tests/Sequence/_var_dump.php b/tests/Sequence/_var_dump.php
index 24f8485..db5d75e 100644
--- a/tests/Sequence/_var_dump.php
+++ b/tests/Sequence/_var_dump.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _var_dump
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testVarDump(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertInstanceDump($expected, $instance);
     }
 }
diff --git a/tests/Sequence/apply.php b/tests/Sequence/apply.php
index f4baebf..9786384 100644
--- a/tests/Sequence/apply.php
+++ b/tests/Sequence/apply.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait apply
 {
-    public function applyDataProvider()
+    public static function applyDataProvider()
     {
         // values, callback
         return [
@@ -22,12 +24,10 @@ public function applyDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider applyDataProvider
-     */
+    #[DataProvider('applyDataProvider')]
     public function testApply(array $values, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $instance->apply($callback);
         $expected = array_map($callback, $values);
@@ -37,7 +37,7 @@ public function testApply(array $values, callable $callback)
 
     public function testApplyCallbackThrowsException()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
 
         try {
             $instance->apply(function($value) {
@@ -53,7 +53,7 @@ public function testApplyCallbackThrowsException()
 
     public function testApplyCallbackThrowsExceptionLaterOn()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
 
         try {
             $instance->apply(function($value) {
@@ -73,7 +73,7 @@ public function testApplyCallbackThrowsExceptionLaterOn()
 
     public function testApplyDoesNotCallByReference()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
 
         $instance->apply(function($value) {
             $before = $value;
diff --git a/tests/Sequence/clear.php b/tests/Sequence/clear.php
index b5cba5f..3c4c361 100644
--- a/tests/Sequence/clear.php
+++ b/tests/Sequence/clear.php
@@ -5,7 +5,7 @@ trait clear
 {
     public function testClear()
     {
-        $instance = $this->getInstance($this->sample());
+        $instance = static::getInstance(self::sample());
         $instance->clear();
 
         $this->assertToArray([], $instance);
diff --git a/tests/Sequence/contains.php b/tests/Sequence/contains.php
index 8694687..02a20ca 100644
--- a/tests/Sequence/contains.php
+++ b/tests/Sequence/contains.php
@@ -1,11 +1,13 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait contains
 {
-    public function containsDataProvider()
+    public static function containsDataProvider()
     {
-        $sample = $this->sample();
+        $sample = self::sample();
 
         // initial, values, expected
         return [
@@ -27,12 +29,10 @@ public function containsDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider containsDataProvider
-     */
+    #[DataProvider('containsDataProvider')]
     public function testContains($initial, array $values, bool $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($expected, $instance->contains(...$values));
     }
 }
diff --git a/tests/Sequence/copy.php b/tests/Sequence/copy.php
index 7e37655..ec9069d 100644
--- a/tests/Sequence/copy.php
+++ b/tests/Sequence/copy.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait copy
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testCopy(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $copy = $instance->copy();
 
         $this->assertEquals($instance->toArray(), $copy->toArray());
diff --git a/tests/Sequence/count.php b/tests/Sequence/count.php
index b6ce778..f4745ec 100644
--- a/tests/Sequence/count.php
+++ b/tests/Sequence/count.php
@@ -5,13 +5,13 @@ trait count
 {
     public function testCount()
     {
-        $instance = $this->getInstance($this->sample());
-        $this->assertCount(count($this->sample()), $instance);
+        $instance = static::getInstance(self::sample());
+        $this->assertCount(count(self::sample()), $instance);
     }
 
     public function testCountEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertCount(0, $instance);
     }
 }
diff --git a/tests/Sequence/filter.php b/tests/Sequence/filter.php
index f320e2d..2ee3752 100644
--- a/tests/Sequence/filter.php
+++ b/tests/Sequence/filter.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait filter
 {
-    public function filterDataProvider()
+    public static function filterDataProvider()
     {
         // values, callback
         return [
@@ -20,12 +22,10 @@ public function filterDataProvider()
     }
 
 
-    /**
-     * @dataProvider filterDataProvider
-     */
+    #[DataProvider('filterDataProvider')]
     public function testFilter(array $values, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $filtered = $instance->filter($callback);
         $expected = array_values(array_filter($values, $callback));
@@ -34,12 +34,10 @@ public function testFilter(array $values, callable $callback)
         $this->assertEquals($expected, $filtered->toArray());
     }
 
-    /**
-     * @dataProvider filterDataProvider
-     */
+    #[DataProvider('filterDataProvider')]
     public function testFilterWithoutCallback(array $values, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $filtered = $instance->filter();
         $expected = array_values(array_filter($values));
@@ -50,7 +48,7 @@ public function testFilterWithoutCallback(array $values, callable $callback)
 
     public function testFilterCallbackThrowsException()
     {
-        $instance = $this->getInstance(["a", "b", "c"]);
+        $instance = static::getInstance(["a", "b", "c"]);
         $filtered = null;
 
         try {
@@ -68,7 +66,7 @@ public function testFilterCallbackThrowsException()
 
     public function testFilterCallbackThrowsExceptionLaterOn()
     {
-        $instance = $this->getInstance(["a", "b", "c"]);
+        $instance = static::getInstance(["a", "b", "c"]);
         $filtered = null;
 
         try {
@@ -89,7 +87,7 @@ public function testFilterCallbackThrowsExceptionLaterOn()
 
     public function testFilterDoesNotLeakWhenCallbackFails()
     {
-        $instance = $this->getInstance(["a", "b", "c"]);
+        $instance = static::getInstance(["a", "b", "c"]);
         $filtered = null;
 
         try {
diff --git a/tests/Sequence/find.php b/tests/Sequence/find.php
index 1fd12f0..98915fe 100644
--- a/tests/Sequence/find.php
+++ b/tests/Sequence/find.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait find
 {
-    public function findDataProvider()
+    public static function findDataProvider()
     {
         // initial, value, expected
         return [
@@ -24,12 +26,10 @@ public function findDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider findDataProvider
-     */
+    #[DataProvider('findDataProvider')]
     public function testFind($initial, $value, $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($expected, $instance->find($value));
     }
 }
diff --git a/tests/Sequence/first.php b/tests/Sequence/first.php
index a1823c8..46e1ad9 100644
--- a/tests/Sequence/first.php
+++ b/tests/Sequence/first.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait first
 {
-    public function firstDataProvider()
+    public static function firstDataProvider()
     {
         // initial, returned
         return [
@@ -13,18 +15,16 @@ public function firstDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider firstDataProvider
-     */
+    #[DataProvider('firstDataProvider')]
     public function testFirst(array $initial, $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($expected, $instance->first());
     }
 
     public function testFirstNowAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->first();
     }
diff --git a/tests/Sequence/get.php b/tests/Sequence/get.php
index 2a64608..95c05c0 100644
--- a/tests/Sequence/get.php
+++ b/tests/Sequence/get.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait get
 {
-    public function getDataProvider()
+    public static function getDataProvider()
     {
         // initial, index, return
         return [
@@ -21,12 +23,10 @@ public function getDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider getDataProvider
-     */
+    #[DataProvider('getDataProvider')]
     public function testGet(array $initial, $index, $return)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $returned = $instance->get($index);
 
@@ -34,53 +34,43 @@ public function testGet(array $initial, $index, $return)
         $this->assertEquals($return, $returned);
     }
 
-    /**
-     * @dataProvider outOfRangeDataProvider
-     */
+    #[DataProvider('outOfRangeDataProvider')]
     public function testGetIndexOutOfRange($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->expectIndexOutOfRangeException();
         $instance->get($index);
     }
 
-    /**
-     * @dataProvider badIndexDataProvider
-     */
+    #[DataProvider('badIndexDataProvider')]
     public function testGetIndexBadIndex($initial, $index)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectWrongIndexTypeException();
         $instance->get($index);
     }
 
 
-    /**
-     * @dataProvider getDataProvider
-     */
+    #[DataProvider('getDataProvider')]
     public function testArrayAccessGet(array $initial, $index, $return)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($return, $instance[$index]);
     }
 
 
-    /**
-     * @dataProvider badIndexDataProvider
-     */
+    #[DataProvider('badIndexDataProvider')]
     public function testArrayAccessGetIndexBadIndex($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->expectWrongIndexTypeException();
         $instance[$index];
     }
 
-    /**
-     * @dataProvider outOfRangeDataProvider
-     */
+    #[DataProvider('outOfRangeDataProvider')]
     public function testArrayAccessGetIndexOutOfRange($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->expectIndexOutOfRangeException();
         $instance[$index];
     }
@@ -88,13 +78,13 @@ public function testArrayAccessGetIndexOutOfRange($initial, $index)
 
     public function testArrayAccessGetByReference()
     {
-        $instance = $this->getInstance([[1]]);
+        $instance = static::getInstance([[1]]);
         $this->assertEquals(1, $instance[0][0]);
     }
 
     public function testArrayAccessGetNullCoalesce()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $this->assertEquals(null, $instance[10] ?? null);
     }
diff --git a/tests/Sequence/insert.php b/tests/Sequence/insert.php
index ed7bab3..afb166d 100644
--- a/tests/Sequence/insert.php
+++ b/tests/Sequence/insert.php
@@ -1,11 +1,13 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait insert
 {
-    public function insertDataProvider()
+    public static function insertDataProvider()
     {
-        $s = $this->sample();
+        $s = self::sample();
 
         $h = count($s) / 2;
 
@@ -30,30 +32,26 @@ public function insertDataProvider()
     }
 
 
-    /**
-     * @dataProvider insertDataProvider
-     */
+    #[DataProvider('insertDataProvider')]
     public function testInsertVariadic(array $initial, $index, array $values)
     {
         $expected = $initial;
         array_splice($expected, $index, 0, $values);
 
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $instance->insert($index, ...$values);
 
         $this->assertEquals(count($expected), count($instance));
         $this->assertToArray($expected, $instance);
     }
 
-    /**
-     * @dataProvider insertDataProvider
-     */
+    #[DataProvider('insertDataProvider')]
     public function testInsert(array $initial, $index, array $values)
     {
         $expected = $initial;
         array_splice($expected, $index, 0, array_reverse($values));
 
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         foreach ($values as $value) {
             $instance->insert($index, $value);
@@ -63,22 +61,18 @@ public function testInsert(array $initial, $index, array $values)
         $this->assertToArray($expected, $instance);
     }
 
-    /**
-     * @dataProvider outOfRangeDataProvider
-     */
+    #[DataProvider('outOfRangeDataProvider')]
     public function testInsertIndexOutOfRange($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->expectIndexOutOfRangeException();
         $instance->insert($index);
     }
 
-    /**
-     * @dataProvider badIndexDataProvider
-     */
+    #[DataProvider('badIndexDataProvider')]
     public function testInsertIndexBadIndex($initial, $index)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectWrongIndexTypeException();
         $instance->insert($index);
     }
diff --git a/tests/Sequence/isEmpty.php b/tests/Sequence/isEmpty.php
index c136212..8694b84 100644
--- a/tests/Sequence/isEmpty.php
+++ b/tests/Sequence/isEmpty.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait isEmpty
 {
-    public function isEmptyDataProvider()
+    public static function isEmptyDataProvider()
     {
         // values, is empty
         return [
@@ -12,18 +14,16 @@ public function isEmptyDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider isEmptyDataProvider
-     */
+    #[DataProvider('isEmptyDataProvider')]
     public function testIsEmpty(array $values, bool $isEmpty)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertEquals($isEmpty, $instance->isEmpty());
     }
 
     public function testIsNotEmptyAfterRemove()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertTrue($instance->isEmpty());
 
         $instance->push('a');
diff --git a/tests/Sequence/join.php b/tests/Sequence/join.php
index 94be662..55f9046 100644
--- a/tests/Sequence/join.php
+++ b/tests/Sequence/join.php
@@ -1,16 +1,18 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait join
 {
-    public function joinDataProvider()
+    public static function joinDataProvider()
     {
         // values, glue
         $data = [];
 
         $glues   = ['', '~', 0, 1, false];
         $lengths = [0, 1, 2, 3, 10];
-        $obj     = $this->getInstance();
+        $obj     = static::getInstance();
 
         foreach ($lengths as $length) {
             foreach ($glues as $glue) {
@@ -23,22 +25,18 @@ public function joinDataProvider()
         return $data;
     }
 
-    /**
-     * @dataProvider joinDataProvider
-     */
+    #[DataProvider('joinDataProvider')]
     public function testJoin(array $values, $glue)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $expected = join($glue, $values);
         $this->assertEquals($expected, $instance->join($glue));
     }
 
-    /**
-     * @dataProvider joinDataProvider
-     */
+    #[DataProvider('joinDataProvider')]
     public function testJoinWithoutGlue(array $values, $glue)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $expected = join($values);
         $this->assertEquals($expected, $instance->join());
     }
diff --git a/tests/Sequence/last.php b/tests/Sequence/last.php
index 44f200f..10eff93 100644
--- a/tests/Sequence/last.php
+++ b/tests/Sequence/last.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait last
 {
-    public function lastDataProvider()
+    public static function lastDataProvider()
     {
         // initial, returned
         return [
@@ -13,18 +15,16 @@ public function lastDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider lastDataProvider
-     */
+    #[DataProvider('lastDataProvider')]
     public function testLast($initial, $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($expected, $instance->last());
     }
 
     public function testLastNotAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->last();
     }
diff --git a/tests/Sequence/map.php b/tests/Sequence/map.php
index c273fea..b30480c 100644
--- a/tests/Sequence/map.php
+++ b/tests/Sequence/map.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait map
 {
-    public function mapDataProvider()
+    public static function mapDataProvider()
     {
         // values, callback
         return [
@@ -23,12 +25,10 @@ public function mapDataProvider()
     }
 
 
-    /**
-     * @dataProvider mapDataProvider
-     */
+    #[DataProvider('mapDataProvider')]
     public function testMap(array $values, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $mapped = $instance->map($callback);
         $expected = array_map($callback, $values);
@@ -39,7 +39,7 @@ public function testMap(array $values, callable $callback)
 
     public function testMapCallbackThrowsException()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $mapped = null;
 
         try {
@@ -57,7 +57,7 @@ public function testMapCallbackThrowsException()
 
     public function testMapCallbackThrowsExceptionLaterOn()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $mapped = null;
 
         try {
@@ -79,7 +79,7 @@ public function testMapCallbackThrowsExceptionLaterOn()
 
     public function testMapDoesNotLeakWhenCallbackFails()
     {
-        $instance = $this->getInstance(["a", "b", "c"]);
+        $instance = static::getInstance(["a", "b", "c"]);
 
         static::expectException(\Exception::class);
 
diff --git a/tests/Sequence/merge.php b/tests/Sequence/merge.php
index d666fb7..91750ae 100644
--- a/tests/Sequence/merge.php
+++ b/tests/Sequence/merge.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait merge
 {
-    public function mergeDataProvider()
+    public static function mergeDataProvider()
     {
         // A, B, expected
         return [
@@ -15,23 +17,19 @@ public function mergeDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider mergeDataProvider
-     */
+    #[DataProvider('mergeDataProvider')]
     public function testMerge(array $initial, array $values, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $this->assertToArray($expected, $instance->merge($values));
         $this->assertToArray($initial, $instance);
     }
 
-    /**
-     * @dataProvider mergeDataProvider
-     */
+    #[DataProvider('mergeDataProvider')]
     public function testMergeWithSelf(array $initial, array $values, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $this->assertToArray(array_merge($initial, $initial), $instance->merge($instance));
         $this->assertToArray($initial, $instance);
diff --git a/tests/Sequence/pop.php b/tests/Sequence/pop.php
index a8a800d..e2edf43 100644
--- a/tests/Sequence/pop.php
+++ b/tests/Sequence/pop.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait pop
 {
-    public function popDataProvider()
+    public static function popDataProvider()
     {
         // initial, expected, returned
         return [
@@ -12,12 +14,10 @@ public function popDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider popDataProvider
-     */
+    #[DataProvider('popDataProvider')]
     public function testPop($initial, array $expected, $returned)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $result = $instance->pop();
 
@@ -26,14 +26,14 @@ public function testPop($initial, array $expected, $returned)
         $this->assertEquals(count($initial) - 1, count($instance));
 
         //
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->pop();
     }
 
     public function testPopAll()
     {
-        $instance = $this->getInstance(range(1, self::MANY));
+        $instance = static::getInstance(range(1, self::MANY));
 
         while ( ! $instance->isEmpty()) {
             $instance->pop();
diff --git a/tests/Sequence/push.php b/tests/Sequence/push.php
index 926e27a..8b90dbf 100644
--- a/tests/Sequence/push.php
+++ b/tests/Sequence/push.php
@@ -1,31 +1,29 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait push
 {
-    public function pushDataProvider()
+    public static function pushDataProvider()
     {
-        return $this->basicDataProvider();
+        return self::basicDataProvider();
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testPushVariadic(array $values, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->push(...$values);
 
         $this->assertToArray($expected, $instance);
         $this->assertEquals(count($expected), count($instance));
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testPush(array $values, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($values as $value) {
             $instance->push($value);
@@ -35,12 +33,10 @@ public function testPush(array $values, array $expected)
         $this->assertEquals(count($expected), count($instance));
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testArrayAccessPush(array $values, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($values as $value) {
             $instance[] = $value;
@@ -50,12 +46,10 @@ public function testArrayAccessPush(array $values, array $expected)
         $this->assertEquals(count($expected), count($instance));
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testArrayAccessPushByMethod(array $values, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($values as $value) {
             $instance->offsetSet(null, $value);
@@ -67,15 +61,15 @@ public function testArrayAccessPushByMethod(array $values, array $expected)
 
     public function testPushCircularReference()
     {
-        $instance = $this->getInstance(['a', 'b', 'c']);
+        $instance = static::getInstance(['a', 'b', 'c']);
         $instance->push($instance);
         $this->assertToArray(['a', 'b', 'c', $instance], $instance);
     }
 
     public function testPushIndirectCircularReference()
     {
-        $a = $this->getInstance();
-        $b = $this->getInstance();
+        $a = static::getInstance();
+        $b = static::getInstance();
 
         $a->push($b);
         $b->push($a);
@@ -86,8 +80,8 @@ public function testPushIndirectCircularReference()
 
     public function testPushDeeperIndirectCircularReference()
     {
-        $a = $this->getInstance();
-        $b = $this->getInstance();
+        $a = static::getInstance();
+        $b = static::getInstance();
 
         $a->push($b);
         $b->push($a);
@@ -104,8 +98,8 @@ public function testPushDeeperIndirectCircularReference()
 
     public function testPushIndirectCircularReferenceAfterUnshifts()
     {
-        $a = $this->getInstance();
-        $b = $this->getInstance();
+        $a = static::getInstance();
+        $b = static::getInstance();
 
         $a->push(...range(1, 5));
         $b->push(...range(1, 5));
diff --git a/tests/Sequence/reduce.php b/tests/Sequence/reduce.php
index 1dd8b8e..9eea1a9 100644
--- a/tests/Sequence/reduce.php
+++ b/tests/Sequence/reduce.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait reduce
 {
-    public function reduceDataProvider()
+    public static function reduceDataProvider()
     {
         // values, initial, callback
         return [
@@ -20,12 +22,10 @@ public function reduceDataProvider()
     }
 
 
-    /**
-     * @dataProvider reduceDataProvider
-     */
+    #[DataProvider('reduceDataProvider')]
     public function testReduce(array $values, $initial, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $reduced = $instance->reduce($callback, $initial);
         $expected = array_reduce($values, $callback, $initial);
@@ -34,12 +34,10 @@ public function testReduce(array $values, $initial, callable $callback)
         $this->assertEquals($expected, $reduced);
     }
 
-    /**
-     * @dataProvider reduceDataProvider
-     */
+    #[DataProvider('reduceDataProvider')]
     public function testReduceWithoutInitial(array $values, $initial, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $reduced = $instance->reduce($callback);
         $expected = array_reduce($values, $callback);
@@ -50,7 +48,7 @@ public function testReduceWithoutInitial(array $values, $initial, callable $call
 
     public function testReduceCallbackThrowsException()
     {
-        $instance = $this->getInstance(["a", "b", "c"]);
+        $instance = static::getInstance(["a", "b", "c"]);
         $result = null;
 
         try {
@@ -68,7 +66,7 @@ public function testReduceCallbackThrowsException()
 
     public function testReduceCallbackThrowsExceptionLaterOn()
     {
-        $instance = $this->getInstance(["a", "b", "c"]);
+        $instance = static::getInstance(["a", "b", "c"]);
         $result = null;
 
         try {
@@ -90,7 +88,7 @@ public function testReduceCallbackThrowsExceptionLaterOn()
 
     public function testReduceCallbackDoesNotLeakOnFailure()
     {
-        $instance = $this->getInstance(["a", "b", "c"]);
+        $instance = static::getInstance(["a", "b", "c"]);
 
         static::expectException(\Exception::class);
 
diff --git a/tests/Sequence/remove.php b/tests/Sequence/remove.php
index 0e61403..ff46fd1 100644
--- a/tests/Sequence/remove.php
+++ b/tests/Sequence/remove.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait remove
 {
-    public function removeDataProvider()
+    public static function removeDataProvider()
     {
         // initial, index, return, expected
         return [
@@ -19,12 +21,10 @@ public function removeDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider removeDataProvider
-     */
+    #[DataProvider('removeDataProvider')]
     public function testRemove($initial, $index, $return, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $returned = $instance->remove($index);
 
         $this->assertEquals(count($initial) - 1, count($instance));
@@ -32,22 +32,18 @@ public function testRemove($initial, $index, $return, array $expected)
         $this->assertEquals($return, $returned);
     }
 
-    /**
-     * @dataProvider outOfRangeDataProvider
-     */
+    #[DataProvider('outOfRangeDataProvider')]
     public function testRemoveIndexOutOfRange($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->expectIndexOutOfRangeException();
         $instance->remove($index);
     }
 
-    /**
-     * @dataProvider badIndexDataProvider
-     */
+    #[DataProvider('badIndexDataProvider')]
     public function testRemoveIndexBadIndex($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->expectWrongIndexTypeException();
         $instance->remove($index);
     }
diff --git a/tests/Sequence/reverse.php b/tests/Sequence/reverse.php
index ee8ce3d..9db63d1 100644
--- a/tests/Sequence/reverse.php
+++ b/tests/Sequence/reverse.php
@@ -1,21 +1,21 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait reverse
 {
-    public function reverseDataProvider()
+    public static function reverseDataProvider()
     {
         return array_map(function($a) { return [$a[0], array_reverse($a[1])]; },
-            $this->basicDataProvider()
+            self::basicDataProvider()
         );
     }
 
-    /**
-     * @dataProvider reverseDataProvider
-     */
+    #[DataProvider('reverseDataProvider')]
     public function testReverse(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $instance->reverse();
 
         $this->assertToArray($expected, $instance);
diff --git a/tests/Sequence/reversed.php b/tests/Sequence/reversed.php
index ec38385..fd97e92 100644
--- a/tests/Sequence/reversed.php
+++ b/tests/Sequence/reversed.php
@@ -1,21 +1,21 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait reversed
 {
-    public function reversedDataProvider()
+    public static function reversedDataProvider()
     {
         return array_map(function($a) { return [$a[0], array_reverse($a[1])]; },
-            $this->basicDataProvider()
+            self::basicDataProvider()
         );
     }
 
-    /**
-     * @dataProvider reversedDataProvider
-     */
+    #[DataProvider('reversedDataProvider')]
     public function testReversed(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertToArray($expected, $instance->reversed());
         $this->assertToArray($values, $instance);
     }
diff --git a/tests/Sequence/rotate.php b/tests/Sequence/rotate.php
index db15605..cba5892 100644
--- a/tests/Sequence/rotate.php
+++ b/tests/Sequence/rotate.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait rotate
 {
-    public function rotateDataProvider()
+    public static function rotateDataProvider()
     {
         // values, rotation, expected
         return [
@@ -41,12 +43,10 @@ public function rotateDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider rotateDataProvider
-     */
+    #[DataProvider('rotateDataProvider')]
     public function testRotate(array $values, int $rotation, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $instance->rotate($rotation);
         $this->assertToArray($expected, $instance);
     }
diff --git a/tests/Sequence/set.php b/tests/Sequence/set.php
index 20e23e7..4a6ac40 100644
--- a/tests/Sequence/set.php
+++ b/tests/Sequence/set.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait set
 {
-    public function setDataProvider()
+    public static function setDataProvider()
     {
         // initial, index, value, expected
         return [
@@ -20,12 +22,10 @@ public function setDataProvider()
     }
 
 
-    /**
-     * @dataProvider setDataProvider
-     */
+    #[DataProvider('setDataProvider')]
     public function testSet($initial, $index, $value, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $instance->set($index, $value);
 
@@ -35,53 +35,43 @@ public function testSet($initial, $index, $value, array $expected)
         $this->assertEquals(count($initial), count($instance));
     }
 
-    /**
-     * @dataProvider outOfRangeDataProvider
-     */
+    #[DataProvider('outOfRangeDataProvider')]
     public function testSetOutOfRange($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->expectIndexOutOfRangeException();
         $instance->set($index, 1);
     }
 
-    /**
-     * @dataProvider badIndexDataProvider
-     */
+    #[DataProvider('badIndexDataProvider')]
     public function testSetIndexBadIndex($initial, $index)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectWrongIndexTypeException();
         $instance->set($index, 1);
     }
 
-    /**
-     * @dataProvider setDataProvider
-     */
+    #[DataProvider('setDataProvider')]
     public function testArrayAccessSet($initial, $index, $value, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $instance[$index] = $value;
         $this->assertToArray($expected, $instance);
         $this->assertEquals(count($expected), count($instance));
     }
 
-    /**
-     * @dataProvider badIndexDataProvider
-     */
+    #[DataProvider('badIndexDataProvider')]
     public function testArrayAccessSetIndexBadIndex($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->expectWrongIndexTypeException();
         $instance[$index] = 1;
     }
 
-    /**
-     * @dataProvider outOfRangeDataProvider
-     */
+    #[DataProvider('outOfRangeDataProvider')]
     public function testArrayAccessSetIndexOutOfRange($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->expectIndexOutOfRangeException();
         $instance[$index] = 1;
     }
@@ -89,7 +79,7 @@ public function testArrayAccessSetIndexOutOfRange($initial, $index)
 
     public function testArrayAccessSetByReference()
     {
-        $instance = $this->getInstance([[1]]);
+        $instance = static::getInstance([[1]]);
         $instance[0][0] = 2;
 
         $this->assertToArray([[2]], $instance);
@@ -97,7 +87,7 @@ public function testArrayAccessSetByReference()
 
     public function testSetWithReference()
     {
-        $instance = $this->getInstance(['a', 'b', 'c']);
+        $instance = static::getInstance(['a', 'b', 'c']);
 
         $key = 1;
         $ref = &$key;
@@ -117,7 +107,7 @@ public function testSetWithReference()
 
     public function testArrayAccessSetWithReference()
     {
-        $instance = $this->getInstance(['a', 'b', 'c']);
+        $instance = static::getInstance(['a', 'b', 'c']);
 
         $key = 1;
         $ref = &$key;
diff --git a/tests/Sequence/shift.php b/tests/Sequence/shift.php
index 8a80dd8..4e3618f 100644
--- a/tests/Sequence/shift.php
+++ b/tests/Sequence/shift.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait shift
 {
-    public function shiftDataProvider()
+    public static function shiftDataProvider()
     {
         // initial, expected, result
         return [
@@ -15,12 +17,10 @@ public function shiftDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider shiftDataProvider
-     */
+    #[DataProvider('shiftDataProvider')]
     public function testShift(array $initial, $expected, array $result)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $this->assertEquals($expected, $instance->shift());
         $this->assertToArray($result, $instance);
@@ -29,14 +29,14 @@ public function testShift(array $initial, $expected, array $result)
 
     public function testShiftNotAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->shift();
     }
 
     public function testShiftAll()
     {
-        $instance = $this->getInstance(range(1, self::MANY));
+        $instance = static::getInstance(range(1, self::MANY));
 
         while ( ! $instance->isEmpty()) {
             $instance->shift();
diff --git a/tests/Sequence/slice.php b/tests/Sequence/slice.php
index d99560f..39f8270 100644
--- a/tests/Sequence/slice.php
+++ b/tests/Sequence/slice.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait slice
 {
-    public function sliceDataProvider()
+    public static function sliceDataProvider()
     {
         $a = ['a', 'b', 'c'];
         $n = count($a);
@@ -21,12 +23,10 @@ public function sliceDataProvider()
     }
 
 
-    /**
-     * @dataProvider sliceDataProvider
-     */
+    #[DataProvider('sliceDataProvider')]
     public function testSlice(array $values, int $index, int $length)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $sliced = $instance->slice($index, $length);
         $expected = array_slice($values, $index, $length);
@@ -35,12 +35,10 @@ public function testSlice(array $values, int $index, int $length)
         $this->assertToArray($expected, $sliced);
     }
 
-    /**
-     * @dataProvider sliceDataProvider
-     */
+    #[DataProvider('sliceDataProvider')]
     public function testSliceWithoutLength(array $values, int $index, int $length)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $sliced = $instance->slice($index);
         $expected = array_slice($values, $index);
@@ -49,12 +47,10 @@ public function testSliceWithoutLength(array $values, int $index, int $length)
         $this->assertToArray($expected, $sliced);
     }
 
-    /**
-     * @dataProvider sliceDataProvider
-     */
+    #[DataProvider('sliceDataProvider')]
     public function testSliceWithLengthNull(array $values, int $index, int $length)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $sliced = $instance->slice($index, null);
         $expected = array_slice($values, $index);
@@ -69,7 +65,7 @@ public function testLargeSliceHalf()
         $x = 0;
         $y = intdiv($n, 2);
 
-        $instance = $this->getInstance(range(0, $n));
+        $instance = static::getInstance(range(0, $n));
 
         $this->assertToArray(range($x, $y - 1), $instance->slice($x, $y));
         $this->assertToArray(range($y, $n),     $instance->slice($y));
@@ -81,7 +77,7 @@ public function testLargeSliceOffset()
         $x = intdiv($n, 4);
         $y = intdiv($n, 4) + intdiv($n, 2);
 
-        $instance = $this->getInstance(range(0, $n));
+        $instance = static::getInstance(range(0, $n));
 
         $this->assertToArray(range($x, $y - 1), $instance->slice($x, $y - $x));
     }
diff --git a/tests/Sequence/sort.php b/tests/Sequence/sort.php
index 254e95f..5a16eea 100644
--- a/tests/Sequence/sort.php
+++ b/tests/Sequence/sort.php
@@ -5,7 +5,7 @@ trait sort
 {
     public function testSort()
     {
-        $instance = $this->getInstance([4, 1, 2, 5, 3]);
+        $instance = static::getInstance([4, 1, 2, 5, 3]);
         $instance->sort();
 
         $this->assertToArray([1, 2, 3, 4, 5], $instance);
@@ -13,7 +13,7 @@ public function testSort()
 
     public function testSortUsingComparator()
     {
-        $instance = $this->getInstance([4, 1, 2, 5, 3]);
+        $instance = static::getInstance([4, 1, 2, 5, 3]);
 
         $instance->sort(function($a, $b) {
             return $b <=> $a;
diff --git a/tests/Sequence/sorted.php b/tests/Sequence/sorted.php
index 832088a..02a5b76 100644
--- a/tests/Sequence/sorted.php
+++ b/tests/Sequence/sorted.php
@@ -5,7 +5,7 @@ trait sorted
 {
     public function testSorted()
     {
-        $instance = $this->getInstance([4, 1, 2, 5, 3]);
+        $instance = static::getInstance([4, 1, 2, 5, 3]);
         $sorted = $instance->sorted();
 
         $this->assertToArray([1, 2, 3, 4, 5], $sorted);
@@ -14,7 +14,7 @@ public function testSorted()
 
     public function testSortedUsingComparator()
     {
-        $instance = $this->getInstance([4, 1, 2, 5, 3]);
+        $instance = static::getInstance([4, 1, 2, 5, 3]);
 
         $sorted = $instance->sorted(function($a, $b) {
             return $b <=> $a;
diff --git a/tests/Sequence/sum.php b/tests/Sequence/sum.php
index 77e4e51..fa95b58 100644
--- a/tests/Sequence/sum.php
+++ b/tests/Sequence/sum.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait sum
 {
-    public function sumDataProvider()
+    public static function sumDataProvider()
     {
         $nonNumbers = version_compare(PHP_VERSION, '8.3.0', '>=') ? [true, false, null] : ["a", true, false, null];
         return [
@@ -28,12 +30,10 @@ public function sumDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider sumDataProvider
-     */
+    #[DataProvider('sumDataProvider')]
     public function testSum($values, $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertEquals($expected, $instance->sum());
     }
 }
diff --git a/tests/Sequence/toArray.php b/tests/Sequence/toArray.php
index 758cfc1..6e0ca1f 100644
--- a/tests/Sequence/toArray.php
+++ b/tests/Sequence/toArray.php
@@ -1,19 +1,19 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait toArray
 {
-    public function toArrayDataProvider()
+    public static function toArrayDataProvider()
     {
-        return $this->basicDataProvider();
+        return self::basicDataProvider();
     }
 
-    /**
-     * @dataProvider toArrayDataProvider
-     */
+    #[DataProvider('toArrayDataProvider')]
     public function testToArray(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertToArray($expected, $instance);
     }
 }
diff --git a/tests/Sequence/unshift.php b/tests/Sequence/unshift.php
index e380fc6..a497509 100644
--- a/tests/Sequence/unshift.php
+++ b/tests/Sequence/unshift.php
@@ -1,19 +1,19 @@
 <?php
 namespace Ds\Tests\Sequence;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait unshift
 {
-    public function unshiftDataProvider()
+    public static function unshiftDataProvider()
     {
-        return $this->basicDataProvider();
+        return self::basicDataProvider();
     }
 
-    /**
-     * @dataProvider unshiftDataProvider
-     */
+    #[DataProvider('unshiftDataProvider')]
     public function testUnshiftVariadic(array $initial, array $values)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $instance->unshift(...$values);
         $expected = array_merge($values, $initial);
@@ -22,12 +22,10 @@ public function testUnshiftVariadic(array $initial, array $values)
         $this->assertEquals(count($expected), count($instance));
     }
 
-    /**
-     * @dataProvider unshiftDataProvider
-     */
+    #[DataProvider('unshiftDataProvider')]
     public function testUnshift(array $initial, array $values)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         foreach ($values as $value) {
             $instance->unshift($value);
diff --git a/tests/Set/__construct.php b/tests/Set/__construct.php
index 27e8779..f737ce1 100644
--- a/tests/Set/__construct.php
+++ b/tests/Set/__construct.php
@@ -1,13 +1,15 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 use Ds\Set;
 
 trait __construct
 {
-    public function constructDataProvider()
+    public static function constructDataProvider()
     {
-        list($unique, $duplicated) = $this->getUniqueAndDuplicateData();
+        list($unique, $duplicated) = self::getUniqueAndDuplicateData();
 
         return [
             [[],            []],
@@ -19,17 +21,13 @@ public function constructDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider constructDataProvider
-     */
+    #[DataProvider('constructDataProvider')]
     public function testConstruct(array $values, array $expected)
     {
         $this->assertToArray($expected, new Set($values));
     }
 
-    /**
-     * @dataProvider constructDataProvider
-     */
+    #[DataProvider('constructDataProvider')]
     public function testConstructUsingIterable(array $values, array $expected)
     {
         $this->assertToArray($expected, new Set(new \ArrayIterator($values)));
diff --git a/tests/Set/_clone.php b/tests/Set/_clone.php
index 5258ff3..b336989 100644
--- a/tests/Set/_clone.php
+++ b/tests/Set/_clone.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _clone
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testClone($values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $clone = clone $instance;
 
diff --git a/tests/Set/_echo.php b/tests/Set/_echo.php
index d656e18..4d845ad 100644
--- a/tests/Set/_echo.php
+++ b/tests/Set/_echo.php
@@ -5,6 +5,6 @@ trait _echo
 {
     public function testEcho()
     {
-        $this->assertInstanceToString($this->getInstance());
+        $this->assertInstanceToString(static::getInstance());
     }
 }
diff --git a/tests/Set/_empty.php b/tests/Set/_empty.php
index d126ca9..cf1270b 100644
--- a/tests/Set/_empty.php
+++ b/tests/Set/_empty.php
@@ -5,7 +5,7 @@ trait _empty
 {
     public function testArrayAccessEmpty()
     {
-        $set = $this->getInstance(['a', 'b', 'c']);
+        $set = static::getInstance(['a', 'b', 'c']);
         $this->expectArrayAccessUnsupportedException();
         empty($set[0]);
     }
diff --git a/tests/Set/_foreach.php b/tests/Set/_foreach.php
index 6943843..ded7fbc 100644
--- a/tests/Set/_foreach.php
+++ b/tests/Set/_foreach.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _foreach
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testForEach(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertForEach($expected, $instance);
     }
 }
diff --git a/tests/Set/_isset.php b/tests/Set/_isset.php
index ce68470..fce021d 100644
--- a/tests/Set/_isset.php
+++ b/tests/Set/_isset.php
@@ -5,14 +5,14 @@ trait _isset
 {
     public function testArrayAccessIsset()
     {
-        $set = $this->getInstance(['a', 'b', 'c']);
+        $set = static::getInstance(['a', 'b', 'c']);
         $this->expectArrayAccessUnsupportedException();
         isset($set[0]);
     }
 
     public function testArrayAccessIssetByMethod()
     {
-        $set = $this->getInstance(['a', 'b', 'c']);
+        $set = static::getInstance(['a', 'b', 'c']);
         $this->expectArrayAccessUnsupportedException();
         $set->offsetExists(0);
     }
diff --git a/tests/Set/_jsonEncode.php b/tests/Set/_jsonEncode.php
index 9cfa4fd..29960a9 100644
--- a/tests/Set/_jsonEncode.php
+++ b/tests/Set/_jsonEncode.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _jsonEncode
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testJsonEncode(array $initial, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals(json_encode($expected), json_encode($instance));
     }
 }
diff --git a/tests/Set/_list.php b/tests/Set/_list.php
index c602181..4d7a913 100644
--- a/tests/Set/_list.php
+++ b/tests/Set/_list.php
@@ -5,7 +5,7 @@ trait _list
 {
     public function testList()
     {
-        $instance = $this->getInstance(['a', 'b', 'c']);
+        $instance = static::getInstance(['a', 'b', 'c']);
         list($a, $b, $c) = $instance;
 
         $this->assertEquals('a', $a);
diff --git a/tests/Set/_serialize.php b/tests/Set/_serialize.php
index bbe55be..6bedfc9 100644
--- a/tests/Set/_serialize.php
+++ b/tests/Set/_serialize.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _serialize
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testSerialize(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertSerialized($expected, $instance, false);
     }
 }
diff --git a/tests/Set/_unset.php b/tests/Set/_unset.php
index a93e1cf..f894a80 100644
--- a/tests/Set/_unset.php
+++ b/tests/Set/_unset.php
@@ -5,14 +5,14 @@ trait _unset
 {
     public function testArrayAccessUnset()
     {
-        $set = $this->getInstance(['a', 'b', 'c']);
+        $set = static::getInstance(['a', 'b', 'c']);
         $this->expectArrayAccessUnsupportedException();
         unset($set[0]);
     }
 
     public function testArrayAccessUnsetByMethod()
     {
-        $set = $this->getInstance();
+        $set = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         $set->offsetUnset('a');
     }
diff --git a/tests/Set/_var_dump.php b/tests/Set/_var_dump.php
index 135a4bb..5533a97 100644
--- a/tests/Set/_var_dump.php
+++ b/tests/Set/_var_dump.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _var_dump
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testVarDump(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertInstanceDump($expected, $instance);
     }
 }
diff --git a/tests/Set/add.php b/tests/Set/add.php
index 8197031..7887828 100644
--- a/tests/Set/add.php
+++ b/tests/Set/add.php
@@ -1,11 +1,13 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait add
 {
-    public function addDataProvider()
+    public static function addDataProvider()
     {
-        list($unique, $duplicates) = $this->getUniqueAndDuplicateData();
+        list($unique, $duplicates) = self::getUniqueAndDuplicateData();
 
         // initial, input, expected
         return [
@@ -40,15 +42,13 @@ public function addDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider addDataProvider
-     */
+    #[DataProvider('addDataProvider')]
     public function testAdd(
         array $initial,
         array $values,
         array $expected
     ) {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         foreach($values as $value) {
             $instance->add($value);
@@ -58,15 +58,13 @@ public function testAdd(
         $this->assertToArray($expected, $instance);
     }
 
-    /**
-     * @dataProvider addDataProvider
-     */
+    #[DataProvider('addDataProvider')]
     public function testArrayAccessAdd(
         array $initial,
         array $values,
         array $expected
     ) {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         foreach($values as $value) {
             $instance[] = $value;
@@ -76,15 +74,13 @@ public function testArrayAccessAdd(
         $this->assertToArray($expected, $instance);
     }
 
-    /**
-     * @dataProvider addDataProvider
-     */
+    #[DataProvider('addDataProvider')]
     public function testArrayAccessAddByMethod(
         array $initial,
         array $values,
         array $expected
     ) {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         foreach($values as $value) {
             $instance->offsetSet(null, $value);
@@ -94,15 +90,13 @@ public function testArrayAccessAddByMethod(
         $this->assertToArray($expected, $instance);
     }
 
-    /**
-     * @dataProvider addDataProvider
-     */
+    #[DataProvider('addDataProvider')]
     public function testAddVariadic(
         array $initial,
         array $values,
         array $expected
     ) {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $instance->add(...$values);
 
         $this->assertEquals(count($expected), count($instance));
@@ -111,15 +105,15 @@ public function testAddVariadic(
 
     public function testAddCircularReference()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->add($instance);
         $this->assertToArray([$instance], $instance);
     }
 
     public function testAddIndirectCircularReference()
     {
-        $a = $this->getInstance();
-        $b = $this->getInstance();
+        $a = static::getInstance();
+        $b = static::getInstance();
 
         $a->add($b);
         $b->add($a);
diff --git a/tests/Set/allocate.php b/tests/Set/allocate.php
index 82610ea..f8f4b03 100644
--- a/tests/Set/allocate.php
+++ b/tests/Set/allocate.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait allocate
 {
-    public function allocateDataProvider()
+    public static function allocateDataProvider()
     {
         $m = \Ds\Set::MIN_CAPACITY;
 
@@ -22,12 +24,10 @@ public function allocateDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider allocateDataProvider
-     */
+    #[DataProvider('allocateDataProvider')]
     public function testAllocate(int $initial, int $allocate, int $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->allocate($initial);
         $instance->allocate($allocate);
diff --git a/tests/Set/capacity.php b/tests/Set/capacity.php
index 9e07e86..73b6741 100644
--- a/tests/Set/capacity.php
+++ b/tests/Set/capacity.php
@@ -9,7 +9,7 @@ public function testCapacity()
     {
         $min = Set::MIN_CAPACITY;
 
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertEquals($min, $instance->capacity());
 
         for ($i = 0; $i < $min; $i++) {
@@ -44,7 +44,7 @@ public function testAutoTruncate()
             0  =>  8,
         ];
 
-        $instance = $this->getInstance(range(1, array_keys($boundaries)[0]));
+        $instance = static::getInstance(range(1, array_keys($boundaries)[0]));
 
         for(;;) {
             if ( ! is_null(($expected = $boundaries[$instance->count()] ?? null))) {
@@ -61,7 +61,7 @@ public function testAutoTruncate()
 
     public function testClearResetsCapacity()
     {
-        $instance = $this->getInstance(range(1, self::MANY));
+        $instance = static::getInstance(range(1, self::MANY));
         $instance->clear();
         $this->assertEquals(Set::MIN_CAPACITY, $instance->capacity());
     }
diff --git a/tests/Set/clear.php b/tests/Set/clear.php
index a698b01..9031772 100644
--- a/tests/Set/clear.php
+++ b/tests/Set/clear.php
@@ -5,7 +5,7 @@ trait clear
 {
     public function testClear()
     {
-        $instance = $this->getInstance($this->sample());
+        $instance = static::getInstance(self::sample());
         $instance->clear();
 
         $this->assertToArray([], $instance);
diff --git a/tests/Set/contains.php b/tests/Set/contains.php
index 84cca10..0b81a4a 100644
--- a/tests/Set/contains.php
+++ b/tests/Set/contains.php
@@ -1,11 +1,13 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait contains
 {
-    public function containsDataProvider()
+    public static function containsDataProvider()
     {
-        list($sample, $duplicates) = $this->getUniqueAndDuplicateData();
+        list($sample, $duplicates) = self::getUniqueAndDuplicateData();
 
         // initial, values, contains
         return [
@@ -25,15 +27,13 @@ public function containsDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider containsDataProvider
-     */
+    #[DataProvider('containsDataProvider')]
     public function testContains(
         array $initial,
         array $values,
         bool  $contains
     ) {
-        $set = $this->getInstance($initial);
+        $set = static::getInstance($initial);
         $this->assertEquals($contains, $set->contains(...$values));
     }
 }
diff --git a/tests/Set/copy.php b/tests/Set/copy.php
index 943a041..d609e57 100644
--- a/tests/Set/copy.php
+++ b/tests/Set/copy.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait copy
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testCopy(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $copy = $instance->copy();
 
         $this->assertEquals($instance->toArray(), $copy->toArray());
diff --git a/tests/Set/count.php b/tests/Set/count.php
index 1692e28..82fa870 100644
--- a/tests/Set/count.php
+++ b/tests/Set/count.php
@@ -5,18 +5,18 @@ trait count
 {
     public function testCount()
     {
-        list($unique, $duplicates) = $this->getUniqueAndDuplicateData();
+        list($unique, $duplicates) = self::getUniqueAndDuplicateData();
 
-        $instance = $this->getInstance($unique);
+        $instance = static::getInstance($unique);
         $this->assertCount(count($unique), $instance);
 
-        $instance = $this->getInstance($duplicates);
+        $instance = static::getInstance($duplicates);
         $this->assertCount(count($unique), $instance);
     }
 
     public function testCountEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertCount(0, $instance);
     }
 }
diff --git a/tests/Set/diff.php b/tests/Set/diff.php
index 6253a12..9b37e1c 100644
--- a/tests/Set/diff.php
+++ b/tests/Set/diff.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait diff
 {
-    public function diffDataProvider()
+    public static function diffDataProvider()
     {
         // Values in A but not in B.
         // A, B, expected result
@@ -17,13 +19,11 @@ public function diffDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider diffDataProvider
-     */
+    #[DataProvider('diffDataProvider')]
     public function testDiff(array $a, array $b, array $expected)
     {
-        $a = $this->getInstance($a);
-        $b = $this->getInstance($b);
+        $a = static::getInstance($a);
+        $b = static::getInstance($b);
 
         $this->assertEquals($expected, $a->diff($b)->toArray());
     }
@@ -33,8 +33,8 @@ public function testDiff(array $a, array $b, array $expected)
     //  */
     // public function testDiffOperator(array $a, array $b, array $expected)
     // {
-    //     $a = $this->getInstance($a);
-    //     $b = $this->getInstance($b);
+    //     $a = static::getInstance($a);
+    //     $b = static::getInstance($b);
 
     //     $this->assertEquals($expected, ($a - $b)->toArray());
     // }
@@ -44,19 +44,17 @@ public function testDiff(array $a, array $b, array $expected)
     //  */
     // public function testDiffOperatorAssign(array $a, array $b, array $expected)
     // {
-    //     $a = $this->getInstance($a);
-    //     $b = $this->getInstance($b);
+    //     $a = static::getInstance($a);
+    //     $b = static::getInstance($b);
 
     //     $a -= $b;
     //     $this->assertEquals($expected, $a->toArray());
     // }
 
-    /**
-     * @dataProvider diffDataProvider
-     */
+    #[DataProvider('diffDataProvider')]
     public function testDiffWithSelf(array $a, array $b, array $expected)
     {
-        $a = $this->getInstance($a);
+        $a = static::getInstance($a);
         $this->assertEquals([], $a->diff($a)->toArray());
     }
 
@@ -65,7 +63,7 @@ public function testDiffWithSelf(array $a, array $b, array $expected)
     //  */
     // public function testDiffOperatorWithSelf(array $a, array $b, array $expected)
     // {
-    //     $a = $this->getInstance($a);
+    //     $a = static::getInstance($a);
     //     $this->assertEquals([], ($a - $a)->toArray());
     // }
 
@@ -74,7 +72,7 @@ public function testDiffWithSelf(array $a, array $b, array $expected)
     //  */
     // public function testDiffOperatorAssignWithSelf(array $a, array $b, array $expected)
     // {
-    //     $a = $this->getInstance($a);
+    //     $a = static::getInstance($a);
 
     //     $a -= $a;
     //     $this->assertEquals([], $a->toArray());
diff --git a/tests/Set/filter.php b/tests/Set/filter.php
index b626173..be27b1e 100644
--- a/tests/Set/filter.php
+++ b/tests/Set/filter.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait filter
 {
-    public function filterDataProvider()
+    public static function filterDataProvider()
     {
         // values, callback
         return [
@@ -14,12 +16,10 @@ public function filterDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider filterDataProvider
-     */
+    #[DataProvider('filterDataProvider')]
     public function testFilter(array $values, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $filtered = $instance->filter($callback);
         $expected = array_values(array_filter($values, $callback));
@@ -28,12 +28,10 @@ public function testFilter(array $values, callable $callback)
         $this->assertEquals($expected, $filtered->toArray());
     }
 
-    /**
-     * @dataProvider filterDataProvider
-     */
+    #[DataProvider('filterDataProvider')]
     public function testFilterWithoutCallback(array $values, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $filtered = $instance->filter();
         $expected = array_values(array_filter($values));
@@ -44,7 +42,7 @@ public function testFilterWithoutCallback(array $values, callable $callback)
 
     public function testFilterCallbackThrowsException()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $filtered = null;
 
         try {
@@ -62,7 +60,7 @@ public function testFilterCallbackThrowsException()
 
     public function testFilterCallbackThrowsExceptionLaterOn()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $filtered = null;
 
         try {
diff --git a/tests/Set/first.php b/tests/Set/first.php
index 58d97d8..2053538 100644
--- a/tests/Set/first.php
+++ b/tests/Set/first.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait first
 {
-    public function firstDataProvider()
+    public static function firstDataProvider()
     {
         // initial, returned
         return [
@@ -13,18 +15,16 @@ public function firstDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider firstDataProvider
-     */
+    #[DataProvider('firstDataProvider')]
     public function testFirst(array $initial, $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($expected, $instance->first());
     }
 
     public function testFirstNowAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->first();
     }
diff --git a/tests/Set/get.php b/tests/Set/get.php
index 7ce2cc3..6fee2c8 100644
--- a/tests/Set/get.php
+++ b/tests/Set/get.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait get
 {
-    public function getDataProvider()
+    public static function getDataProvider()
     {
         // initial, index, return
         return [
@@ -21,12 +23,10 @@ public function getDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider getDataProvider
-     */
+    #[DataProvider('getDataProvider')]
     public function testGet(array $initial, $index, $return)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $returned = $instance->get($index);
 
@@ -34,67 +34,55 @@ public function testGet(array $initial, $index, $return)
         $this->assertEquals($return, $returned);
     }
 
-    /**
-     * @dataProvider outOfRangeDataProvider
-     */
+    #[DataProvider('outOfRangeDataProvider')]
     public function testGetIndexOutOfRange($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->expectIndexOutOfRangeException();
         $instance->get($index);
     }
 
-    /**
-     * @dataProvider badIndexDataProvider
-     */
+    #[DataProvider('badIndexDataProvider')]
     public function testGetIndexBadIndex($initial, $index)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectWrongIndexTypeException();
         $instance->get($index);
     }
 
-    /**
-     * @dataProvider getDataProvider
-     */
+    #[DataProvider('getDataProvider')]
     public function testArrayAccessGet(array $initial, $index, $return)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($return, $instance[$index]);
     }
 
-    /**
-     * @dataProvider getDataProvider
-     */
+    #[DataProvider('getDataProvider')]
     public function testArrayAccessGetByMethod(array $initial, $index, $return)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($return, $instance->offsetGet($index));
     }
 
-    /**
-     * @dataProvider badIndexDataProvider
-     */
+    #[DataProvider('badIndexDataProvider')]
     public function testArrayAccessGetIndexBadIndex($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->expectWrongIndexTypeException();
         $instance[$index];
     }
 
-    /**
-     * @dataProvider outOfRangeDataProvider
-     */
+    #[DataProvider('outOfRangeDataProvider')]
     public function testArrayAccessGetIndexOutOfRange($initial, $index)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->expectIndexOutOfRangeException();
         $instance[$index];
     }
 
     public function testGetFirstAfterRemove()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->add('a', 'b', 'c');
         $this->assertEquals('a', $instance->get(0));
@@ -108,7 +96,7 @@ public function testGetFirstAfterRemove()
 
     public function testGetLastAfterRemove()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->add('a', 'b', 'c');
         $this->assertEquals('c', $instance->get(2));
@@ -120,7 +108,7 @@ public function testGetLastAfterRemove()
         $this->assertEquals('a', $instance->get(0));
     }
 
-    public function getAfterRemoveProvider()
+    public static function getAfterRemoveProvider()
     {
         // values, value to remove, get index, expected result
         return [
@@ -135,12 +123,10 @@ public function getAfterRemoveProvider()
         ];
     }
 
-    /**
-     * @dataProvider getAfterRemoveProvider
-     */
+    #[DataProvider('getAfterRemoveProvider')]
     public function testGetAfterRemove(array $values, $remove, $index, $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $instance->remove($remove);
 
         $this->assertEquals($expected, $instance->get($index));
@@ -148,7 +134,7 @@ public function testGetAfterRemove(array $values, $remove, $index, $expected)
 
     public function testGetAfterRemoveAtTheStart()
     {
-        $instance = $this->getInstance(['a', 'b', 'c', 'd', 'e']);
+        $instance = static::getInstance(['a', 'b', 'c', 'd', 'e']);
 
         $instance->remove('a');
         $this->assertEquals('b', $instance->get(0));
@@ -174,7 +160,7 @@ public function testGetAfterRemoveAtTheStart()
 
     public function testGetAfterRemoveAtTheEnd()
     {
-        $instance = $this->getInstance(['a', 'b', 'c', 'd', 'e']);
+        $instance = static::getInstance(['a', 'b', 'c', 'd', 'e']);
 
         $instance->remove('e');
         $this->assertEquals('a', $instance->get(0));
@@ -200,7 +186,7 @@ public function testGetAfterRemoveAtTheEnd()
 
     public function testGetAfterMultipleRemoveAtEitherEnd()
     {
-        $instance = $this->getInstance(['a', 'b', 'c', 'd', 'e']);
+        $instance = static::getInstance(['a', 'b', 'c', 'd', 'e']);
 
         $instance->remove('a');
         $this->assertEquals('b', $instance->get(0));
diff --git a/tests/Set/intersect.php b/tests/Set/intersect.php
index 9e03c86..cc5b991 100644
--- a/tests/Set/intersect.php
+++ b/tests/Set/intersect.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait intersect
 {
-    public function intersectDataProvider()
+    public static function intersectDataProvider()
     {
         // Values in A that are also in B.
         // A, B, expected result
@@ -17,23 +19,19 @@ public function intersectDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider intersectDataProvider
-     */
+    #[DataProvider('intersectDataProvider')]
     public function testIntersect(array $initial, array $values, array $expected)
     {
-        $a = $this->getInstance($initial);
-        $b = $this->getInstance($values);
+        $a = static::getInstance($initial);
+        $b = static::getInstance($values);
 
         $this->assertEquals($expected, $a->intersect($b)->toArray());
     }
 
-    /**
-     * @dataProvider intersectDataProvider
-     */
+    #[DataProvider('intersectDataProvider')]
     public function testIntersectWithSelf(array $initial, array $values, array $expected)
     {
-        $a = $this->getInstance($initial);
+        $a = static::getInstance($initial);
         $this->assertEquals($initial, $a->intersect($a)->toArray());
     }
 
@@ -42,8 +40,8 @@ public function testIntersectWithSelf(array $initial, array $values, array $expe
      */
     public function testIntersectContains()
     {
-        $ab = $this->getInstance(["a", "b"]);
-        $bc = $this->getInstance(["b", "c"]);
+        $ab = static::getInstance(["a", "b"]);
+        $bc = static::getInstance(["b", "c"]);
 
         $b = $ab->intersect($bc);
 
@@ -59,8 +57,8 @@ public function testIntersectContains()
      */
     public function testIntersectAdd()
     {
-        $ab = $this->getInstance(["a", "b"]);
-        $bc = $this->getInstance(["b", "c"]);
+        $ab = static::getInstance(["a", "b"]);
+        $bc = static::getInstance(["b", "c"]);
 
         $b = $ab->intersect($bc);
         $b->add("b");
@@ -73,8 +71,8 @@ public function testIntersectAdd()
     //  */
     // public function testIntersectOperator(array $initial, array $values, array $expected)
     // {
-    //     $a = $this->getInstance($initial);
-    //     $b = $this->getInstance($values);
+    //     $a = static::getInstance($initial);
+    //     $b = static::getInstance($values);
 
     //     $this->assertEquals($expected, ($a & $b)->toArray());
     // }
@@ -84,8 +82,8 @@ public function testIntersectAdd()
     //  */
     // public function testIntersectOperatorAssign(array $initial, array $values, array $expected)
     // {
-    //     $a = $this->getInstance($initial);
-    //     $b = $this->getInstance($values);
+    //     $a = static::getInstance($initial);
+    //     $b = static::getInstance($values);
 
     //     $a &= $b;
     //     $this->assertEquals($expected, $a->toArray());
@@ -96,7 +94,7 @@ public function testIntersectAdd()
     //  */
     // public function testIntersectOperatorWithSelf(array $initial, array $values, array $expected)
     // {
-    //     $a = $this->getInstance($initial);
+    //     $a = static::getInstance($initial);
     //     $this->assertEquals($initial, ($a & $a)->toArray());
     // }
 
@@ -105,7 +103,7 @@ public function testIntersectAdd()
     //  */
     // public function testIntersectOperatorAssignWithSelf(array $initial, array $values, array $expected)
     // {
-    //     $a = $this->getInstance($initial);
+    //     $a = static::getInstance($initial);
 
     //     $a &= $a;
     //     $this->assertEquals($initial, $a->toArray());
diff --git a/tests/Set/isEmpty.php b/tests/Set/isEmpty.php
index 26d908c..cf8377d 100644
--- a/tests/Set/isEmpty.php
+++ b/tests/Set/isEmpty.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait isEmpty
 {
-    public function isEmptyDataProvider()
+    public static function isEmptyDataProvider()
     {
         // values, is empty
         return [
@@ -12,18 +14,16 @@ public function isEmptyDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider isEmptyDataProvider
-     */
+    #[DataProvider('isEmptyDataProvider')]
     public function testIsEmpty(array $values, bool $isEmpty)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertEquals($isEmpty, $instance->isEmpty());
     }
 
     public function testIsNotEmptyAfterRemove()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertTrue($instance->isEmpty());
 
         $instance->add('a');
diff --git a/tests/Set/join.php b/tests/Set/join.php
index 7b09e7b..3e3a81e 100644
--- a/tests/Set/join.php
+++ b/tests/Set/join.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait join
 {
-    public function joinDataProvider()
+    public static function joinDataProvider()
     {
         // values, glue
         $data = [];
@@ -20,22 +22,18 @@ public function joinDataProvider()
         return $data;
     }
 
-    /**
-     * @dataProvider joinDataProvider
-     */
+    #[DataProvider('joinDataProvider')]
     public function testJoin(array $values, $glue)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $expected = join($glue, $values);
         $this->assertEquals($expected, $instance->join($glue));
     }
 
-    /**
-     * @dataProvider joinDataProvider
-     */
+    #[DataProvider('joinDataProvider')]
     public function testJoinWithoutGlue(array $values, $glue)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $expected = join($values);
         $this->assertEquals($expected, $instance->join());
     }
diff --git a/tests/Set/last.php b/tests/Set/last.php
index 67d45a5..2e31d64 100644
--- a/tests/Set/last.php
+++ b/tests/Set/last.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait last
 {
-    public function lastDataProvider()
+    public static function lastDataProvider()
     {
         // initial, returned
         return [
@@ -13,18 +15,16 @@ public function lastDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider lastDataProvider
-     */
+    #[DataProvider('lastDataProvider')]
     public function testLast($initial, $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals($expected, $instance->last());
     }
 
     public function testLastNotAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->last();
     }
diff --git a/tests/Set/map.php b/tests/Set/map.php
index bbbe75a..a6ab43f 100644
--- a/tests/Set/map.php
+++ b/tests/Set/map.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait map
 {
-    public function mapDataProvider()
+    public static function mapDataProvider()
     {
         // values, callback
         return [
@@ -23,12 +25,10 @@ public function mapDataProvider()
     }
 
 
-    /**
-     * @dataProvider mapDataProvider
-     */
+    #[DataProvider('mapDataProvider')]
     public function testMap(array $values, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $mapped = $instance->map($callback);
         $expected = array_unique(array_map($callback, $values));
@@ -39,7 +39,7 @@ public function testMap(array $values, callable $callback)
 
     public function testMapCallbackThrowsException()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $mapped = null;
 
         try {
@@ -57,7 +57,7 @@ public function testMapCallbackThrowsException()
 
     public function testMapCallbackThrowsExceptionLaterOn()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $mapped = null;
 
         try {
@@ -79,7 +79,7 @@ public function testMapCallbackThrowsExceptionLaterOn()
 
     public function testMapDoesNotLeakWhenCallbackFails()
     {
-        $instance = $this->getInstance(["a", "b", "c"]);
+        $instance = static::getInstance(["a", "b", "c"]);
 
         static::expectException(\Exception::class);
 
diff --git a/tests/Set/merge.php b/tests/Set/merge.php
index b1c27ee..538493d 100644
--- a/tests/Set/merge.php
+++ b/tests/Set/merge.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait merge
 {
-    public function mergeDataProvider()
+    public static function mergeDataProvider()
     {
         // A, B, expected
         return [
@@ -15,23 +17,19 @@ public function mergeDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider mergeDataProvider
-     */
+    #[DataProvider('mergeDataProvider')]
     public function testMerge(array $initial, array $values, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $this->assertToArray($expected, $instance->merge($values));
         $this->assertToArray($initial, $instance);
     }
 
-    /**
-     * @dataProvider mergeDataProvider
-     */
+    #[DataProvider('mergeDataProvider')]
     public function testMergeWithSelf(array $initial, array $values, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $this->assertToArray($initial, $instance->merge($instance));
         $this->assertToArray($initial, $instance);
diff --git a/tests/Set/reduce.php b/tests/Set/reduce.php
index 2fe10cb..5ef98ca 100644
--- a/tests/Set/reduce.php
+++ b/tests/Set/reduce.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait reduce
 {
-    public function reduceDataProvider()
+    public static function reduceDataProvider()
     {
         // values, initial, callback
         return [
@@ -19,12 +21,10 @@ public function reduceDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider reduceDataProvider
-     */
+    #[DataProvider('reduceDataProvider')]
     public function testReduce(array $values, $initial, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $reduced = $instance->reduce($callback, $initial);
         $expected = array_reduce($values, $callback, $initial);
@@ -33,12 +33,10 @@ public function testReduce(array $values, $initial, callable $callback)
         $this->assertEquals($expected, $reduced);
     }
 
-    /**
-     * @dataProvider reduceDataProvider
-     */
+    #[DataProvider('reduceDataProvider')]
     public function testReduceWithoutInitial(array $values, $initial, callable $callback)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $reduced = $instance->reduce($callback);
         $expected = array_reduce($values, $callback);
@@ -49,7 +47,7 @@ public function testReduceWithoutInitial(array $values, $initial, callable $call
 
     public function testReduceCallbackThrowsException()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $result = null;
 
         try {
@@ -67,7 +65,7 @@ public function testReduceCallbackThrowsException()
 
     public function testReduceCallbackThrowsExceptionLaterOn()
     {
-        $instance = $this->getInstance([1, 2, 3]);
+        $instance = static::getInstance([1, 2, 3]);
         $result = null;
 
         try {
diff --git a/tests/Set/remove.php b/tests/Set/remove.php
index a6f6b4d..2482865 100644
--- a/tests/Set/remove.php
+++ b/tests/Set/remove.php
@@ -1,11 +1,13 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait remove
 {
-    public function removeDataProvider()
+    public static function removeDataProvider()
     {
-        list($unique, $duplicates) = $this->getUniqueAndDuplicateData();
+        list($unique, $duplicates) = self::getUniqueAndDuplicateData();
 
         // initial, values to remove, expected.
         return [
@@ -34,15 +36,13 @@ public function removeDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider removeDataProvider
-     */
+    #[DataProvider('removeDataProvider')]
     public function testRemove(
         array $initial,
         array $values,
         array $expected
     ) {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         foreach ($values as $value) {
             $instance->remove($value);
@@ -59,15 +59,13 @@ public function testRemove(
         }
     }
 
-    /**
-     * @dataProvider removeDataProvider
-     */
+    #[DataProvider('removeDataProvider')]
     public function testRemoveVariadic(
         array $initial,
         array $values,
         array $expected
     ) {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $instance->remove(...$values);
 
         $this->assertEquals(count($expected), count($instance));
diff --git a/tests/Set/reverse.php b/tests/Set/reverse.php
index 458179f..7c06fc0 100644
--- a/tests/Set/reverse.php
+++ b/tests/Set/reverse.php
@@ -1,21 +1,21 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait reverse
 {
-    public function reverseDataProvider()
+    public static function reverseDataProvider()
     {
         return array_map(function($a) { return [$a[0], array_reverse($a[1])]; },
-            $this->basicDataProvider()
+            self::basicDataProvider()
         );
     }
 
-    /**
-     * @dataProvider reverseDataProvider
-     */
+    #[DataProvider('reverseDataProvider')]
     public function testReverse(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $instance->reverse();
 
         $this->assertToArray($expected, $instance);
diff --git a/tests/Set/reversed.php b/tests/Set/reversed.php
index 2ac5d2a..a10d034 100644
--- a/tests/Set/reversed.php
+++ b/tests/Set/reversed.php
@@ -1,21 +1,21 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait reversed
 {
-    public function reversedDataProvider()
+    public static function reversedDataProvider()
     {
         return array_map(function($a) { return [$a[0], array_reverse($a[1])]; },
-            $this->basicDataProvider()
+            self::basicDataProvider()
         );
     }
 
-    /**
-     * @dataProvider reversedDataProvider
-     */
+    #[DataProvider('reversedDataProvider')]
     public function testReversed(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $reversed = $instance->reversed();
 
         $this->assertToArray($expected, $reversed);
diff --git a/tests/Set/slice.php b/tests/Set/slice.php
index fa08d78..2b9d8d2 100644
--- a/tests/Set/slice.php
+++ b/tests/Set/slice.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait slice
 {
-    public function sliceDataProvider()
+    public static function sliceDataProvider()
     {
         $a = ['a', 'b', 'c'];
         $n = count($a);
@@ -20,12 +22,10 @@ public function sliceDataProvider()
         return $data;
     }
 
-    /**
-     * @dataProvider sliceDataProvider
-     */
+    #[DataProvider('sliceDataProvider')]
     public function testSlice(array $values, int $index, int $length)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $sliced = $instance->slice($index, $length);
         $expected = array_slice($values, $index, $length);
@@ -34,12 +34,10 @@ public function testSlice(array $values, int $index, int $length)
         $this->assertToArray($expected, $sliced);
     }
 
-    /**
-     * @dataProvider sliceDataProvider
-     */
+    #[DataProvider('sliceDataProvider')]
     public function testSliceWithoutLength(array $values, int $index, int $length)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $sliced = $instance->slice($index);
         $expected = array_slice($values, $index, null);
@@ -48,12 +46,10 @@ public function testSliceWithoutLength(array $values, int $index, int $length)
         $this->assertToArray($expected, $sliced);
     }
 
-    /**
-     * @dataProvider sliceDataProvider
-     */
+    #[DataProvider('sliceDataProvider')]
     public function testSliceWithLengthNull(array $values, int $index, int $length)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $sliced = $instance->slice($index, null);
         $expected = array_slice($values, $index, null);
@@ -64,7 +60,7 @@ public function testSliceWithLengthNull(array $values, int $index, int $length)
 
     public function testSliceAfterRemoveOutsideOfSlice()
     {
-        $instance = $this->getInstance(['a', 'b', 'c', 'd', 'e']);
+        $instance = static::getInstance(['a', 'b', 'c', 'd', 'e']);
         $instance->remove('d');
 
         $this->assertToArray(['a', 'b', 'c'], $instance->slice(0, 3));
@@ -72,7 +68,7 @@ public function testSliceAfterRemoveOutsideOfSlice()
 
     public function testSliceAfterRemoveAtStartOfSlice()
     {
-        $instance = $this->getInstance(['a', 'b', 'c', 'd', 'e']);
+        $instance = static::getInstance(['a', 'b', 'c', 'd', 'e']);
         $instance->remove('b');
 
         $this->assertToArray(['c', 'd', 'e'], $instance->slice(1));
@@ -80,7 +76,7 @@ public function testSliceAfterRemoveAtStartOfSlice()
 
     public function testSliceAfterRemoveWithinSlice()
     {
-        $instance = $this->getInstance(['a', 'b', 'c', 'd', 'e']);
+        $instance = static::getInstance(['a', 'b', 'c', 'd', 'e']);
         $instance->remove('c');
 
         $this->assertToArray(['b', 'd', 'e'], $instance->slice(1));
@@ -92,7 +88,7 @@ public function testLargeSliceHalf()
         $x = 0;
         $y = intdiv($n, 2);
 
-        $instance = $this->getInstance(range(0, $n));
+        $instance = static::getInstance(range(0, $n));
 
         $this->assertToArray(range($x, $y - 1), $instance->slice($x, $y));
         $this->assertToArray(range($y, $n),     $instance->slice($y));
@@ -104,7 +100,7 @@ public function testLargeSliceOffset()
         $x = intdiv($n, 4);
         $y = intdiv($n, 4) + intdiv($n, 2);
 
-        $instance = $this->getInstance(range(0, $n));
+        $instance = static::getInstance(range(0, $n));
 
         $this->assertToArray(range($x, $y - 1), $instance->slice($x, $y - $x));
     }
diff --git a/tests/Set/sort.php b/tests/Set/sort.php
index b2a5bcf..9c805bb 100644
--- a/tests/Set/sort.php
+++ b/tests/Set/sort.php
@@ -5,7 +5,7 @@ trait sort
 {
     public function testSort()
     {
-        $instance = $this->getInstance([4, 1, 2, 5, 3]);
+        $instance = static::getInstance([4, 1, 2, 5, 3]);
 
         $instance->sort();
         $this->assertToArray([1, 2, 3, 4, 5], $instance);
@@ -13,7 +13,7 @@ public function testSort()
 
     public function testSortUsingComparator()
     {
-        $instance = $this->getInstance([4, 1, 2, 5, 3]);
+        $instance = static::getInstance([4, 1, 2, 5, 3]);
 
         $instance->sort(function($a, $b) {
             return $b <=> $a;
diff --git a/tests/Set/sorted.php b/tests/Set/sorted.php
index 586e921..0db5d5f 100644
--- a/tests/Set/sorted.php
+++ b/tests/Set/sorted.php
@@ -5,7 +5,7 @@ trait sorted
 {
     public function testSorted()
     {
-        $instance = $this->getInstance([4, 1, 2, 5, 3]);
+        $instance = static::getInstance([4, 1, 2, 5, 3]);
 
         $sorted = $instance->sorted();
 
@@ -15,7 +15,7 @@ public function testSorted()
 
     public function testSortedUsingComparator()
     {
-        $instance = $this->getInstance([4, 1, 2, 5, 3]);
+        $instance = static::getInstance([4, 1, 2, 5, 3]);
 
         $sorted = $instance->sorted(function($a, $b) {
             return $b <=> $a;
diff --git a/tests/Set/sum.php b/tests/Set/sum.php
index ce4a621..f474105 100644
--- a/tests/Set/sum.php
+++ b/tests/Set/sum.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait sum
 {
-    public function sumDataProvider()
+    public static function sumDataProvider()
     {
         $nonNumbers = version_compare(PHP_VERSION, '8.3.0', '>=') ? [true, false, null] : ["a", true, false, null];
         return [
@@ -28,12 +30,10 @@ public function sumDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider sumDataProvider
-     */
+    #[DataProvider('sumDataProvider')]
     public function testSum($values, $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertEquals($expected, $instance->sum());
     }
 }
diff --git a/tests/Set/toArray.php b/tests/Set/toArray.php
index 86efc91..aaf21f1 100644
--- a/tests/Set/toArray.php
+++ b/tests/Set/toArray.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait toArray
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testToArray(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertToArray($expected, $instance);
     }
 }
diff --git a/tests/Set/union.php b/tests/Set/union.php
index 776b8b1..0f5618f 100644
--- a/tests/Set/union.php
+++ b/tests/Set/union.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait union
 {
-    public function unionDataProvider()
+    public static function unionDataProvider()
     {
         // Values in A and values in B.
         // A, B, expected result
@@ -16,23 +18,19 @@ public function unionDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider unionDataProvider
-     */
+    #[DataProvider('unionDataProvider')]
     public function testUnion(array $initial, array $values, array $expected)
     {
-        $a = $this->getInstance($initial);
-        $b = $this->getInstance($values);
+        $a = static::getInstance($initial);
+        $b = static::getInstance($values);
 
         $this->assertEquals($expected, $a->union($b)->toArray());
     }
 
-    /**
-     * @dataProvider unionDataProvider
-     */
+    #[DataProvider('unionDataProvider')]
     public function testUnionWithSelf(array $initial, array $values, array $expected)
     {
-        $a = $this->getInstance($initial);
+        $a = static::getInstance($initial);
         $this->assertEquals($initial, $a->union($a)->toArray());
     }
 
@@ -41,8 +39,8 @@ public function testUnionWhenOperatingOnSetsWithObjectsWithNonZeroHash()
         $a = new \Ds\Tests\HashableObject("a", rand());
         $b = new \Ds\Tests\HashableObject("b", rand());
 
-        $setA = $this->getInstance([$a]);
-        $setB = $this->getInstance([$b]);
+        $setA = static::getInstance([$a]);
+        $setB = static::getInstance([$b]);
 
         $this->assertToArray([$a, $b], $setA->union($setB));
     }
@@ -52,8 +50,8 @@ public function testUnionWhenOperatingOnSetsWithObjectsWithZeroHash()
         $a = new \Ds\Tests\HashableObject("a", 0);
         $b = new \Ds\Tests\HashableObject("b", 0);
 
-        $setA = $this->getInstance([$a]);
-        $setB = $this->getInstance([$b]);
+        $setA = static::getInstance([$a]);
+        $setB = static::getInstance([$b]);
 
         $this->assertToArray([$a, $b], $setA->union($setB));
     }
@@ -63,8 +61,8 @@ public function testUnionWhenOperatingOnSetsWithObjectsWithZeroHash()
     //  */
     // public function testUnionOperator(array $initial, array $values, array $expected)
     // {
-    //     $a = $this->getInstance($initial);
-    //     $b = $this->getInstance($values);
+    //     $a = static::getInstance($initial);
+    //     $b = static::getInstance($values);
 
     //     $this->assertEquals($expected, ($a | $b)->toArray());
     // }
@@ -74,8 +72,8 @@ public function testUnionWhenOperatingOnSetsWithObjectsWithZeroHash()
     //  */
     // public function testUnionOperatorAssign(array $initial, array $values, array $expected)
     // {
-    //     $a = $this->getInstance($initial);
-    //     $b = $this->getInstance($values);
+    //     $a = static::getInstance($initial);
+    //     $b = static::getInstance($values);
 
     //     $a |= $b;
     //     $this->assertEquals($expected, $a->toArray());
@@ -86,7 +84,7 @@ public function testUnionWhenOperatingOnSetsWithObjectsWithZeroHash()
     //  */
     // public function testUnionOperatorWithSelf(array $initial, array $values, array $expected)
     // {
-    //     $a = $this->getInstance($initial);
+    //     $a = static::getInstance($initial);
     //     $this->assertEquals($initial, ($a | $a)->toArray());
     // }
 
@@ -95,7 +93,7 @@ public function testUnionWhenOperatingOnSetsWithObjectsWithZeroHash()
     //  */
     // public function testUnionOperatorAssignWithSelf(array $initial, array $values, array $expected)
     // {
-    //     $a = $this->getInstance($initial);
+    //     $a = static::getInstance($initial);
 
     //     $a |= $a;
     //     $this->assertEquals($initial, $a->toArray());
diff --git a/tests/Set/xor_.php b/tests/Set/xor_.php
index 79071ce..b48c6d6 100644
--- a/tests/Set/xor_.php
+++ b/tests/Set/xor_.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Set;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait xor_
 {
-    public function xorDataProvider()
+    public static function xorDataProvider()
     {
         // Values in either A or B, but not both.
         // A, B, expected result
@@ -15,23 +17,19 @@ public function xorDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider xorDataProvider
-     */
+    #[DataProvider('xorDataProvider')]
     public function testXor(array $a, array $b, array $expected)
     {
-        $a = $this->getInstance($a);
-        $b = $this->getInstance($b);
+        $a = static::getInstance($a);
+        $b = static::getInstance($b);
 
         $this->assertEquals($expected, $a->xor($b)->toArray());
     }
 
-    /**
-     * @dataProvider xorDataProvider
-     */
+    #[DataProvider('xorDataProvider')]
     public function testXorWithSelf(array $a, array $b, array $expected)
     {
-        $a = $this->getInstance($a);
+        $a = static::getInstance($a);
         $this->assertEquals([], $a->xor($a)->toArray());
     }
 
@@ -40,8 +38,8 @@ public function testXorWithSelf(array $a, array $b, array $expected)
      */
     public function testXorAfterDiff()
     {
-        $a = $this->getInstance(['guest', 'member']);
-        $b = $this->getInstance(['member', 'nothing']);
+        $a = static::getInstance(['guest', 'member']);
+        $b = static::getInstance(['member', 'nothing']);
 
         $k = $a->diff($b);  // [guest]
         $x = $a->xor($k);   // [guest, member] ^ [guest] = [member]
@@ -54,8 +52,8 @@ public function testXorAfterDiff()
     //  */
     // public function testXorOperator(array $a, array $b, array $expected)
     // {
-    //     $a = $this->getInstance($a);
-    //     $b = $this->getInstance($b);
+    //     $a = static::getInstance($a);
+    //     $b = static::getInstance($b);
 
     //     $this->assertEquals($expected, ($a ^ $b)->toArray());
     // }
@@ -65,8 +63,8 @@ public function testXorAfterDiff()
     //  */
     // public function testXorOperatorAssign(array $a, array $b, array $expected)
     // {
-    //     $a = $this->getInstance($a);
-    //     $b = $this->getInstance($b);
+    //     $a = static::getInstance($a);
+    //     $b = static::getInstance($b);
 
     //     $a ^= $b;
     //     $this->assertEquals($expected, $a->toArray());
@@ -77,7 +75,7 @@ public function testXorAfterDiff()
     //  */
     // public function testXorOperatorWithSelf(array $a, array $b, array $expected)
     // {
-    //     $a = $this->getInstance($a);
+    //     $a = static::getInstance($a);
     //     $this->assertEquals([], ($a ^ $a)->toArray());
     // }
 
@@ -86,7 +84,7 @@ public function testXorAfterDiff()
     //  */
     // public function testXorOperatorAssignWithSelf(array $a, array $b, array $expected)
     // {
-    //     $a = $this->getInstance($a);
+    //     $a = static::getInstance($a);
 
     //     $a ^= $a;
     //     $this->assertEquals([], $a->toArray());
diff --git a/tests/SetTest.php b/tests/SetTest.php
index c6a552b..d1d4ced 100644
--- a/tests/SetTest.php
+++ b/tests/SetTest.php
@@ -3,7 +3,7 @@
 
 use ArrayAccess;
 
-class SetTest extends CollectionTest
+class SetTest extends CollectionTestCase
 {
     use Set\__construct;
     use Set\_clone;
@@ -46,14 +46,14 @@ class SetTest extends CollectionTest
     use Set\union;
     use Set\xor_;
 
-    public function getInstance(array $values = [])
+    public static function getInstance(array $values = [])
     {
         return new \Ds\Set($values);
     }
 
-    public function getUniqueAndDuplicateData()
+    public static function getUniqueAndDuplicateData()
     {
-        $sample = $this->sample();
+        $sample = self::sample();
         $duplicates = [];
 
         foreach ($sample as $value) {
@@ -71,14 +71,14 @@ public function getUniqueAndDuplicateData()
 
     public function testArrayAccessSet()
     {
-        $set = $this->getInstance();
+        $set = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         $set['a'] = 1;
     }
 
     public function testImplementsArrayAccess()
     {
-        $this->assertInstanceOf(ArrayAccess::class, $this->getInstance());
+        $this->assertInstanceOf(ArrayAccess::class, static::getInstance());
     }
 
     /**
diff --git a/tests/Stack/__construct.php b/tests/Stack/__construct.php
index 5272ebd..0745087 100644
--- a/tests/Stack/__construct.php
+++ b/tests/Stack/__construct.php
@@ -1,32 +1,30 @@
 <?php
 namespace Ds\Tests\Stack;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 use Ds\Stack;
 
 trait __construct
 {
-    public function constructDataProvider()
+    public static function constructDataProvider()
     {
         return [
             [[]],
             [['a']],
             [['a', 'a']],
             [['a', 'b']],
-            [$this->sample()],
+            [self::sample()],
         ];
     }
 
-    /**
-     * @dataProvider constructDataProvider
-     */
+    #[DataProvider('constructDataProvider')]
     public function testConstruct(array $values)
     {
         $this->assertToArray(array_reverse($values), new Stack($values));
     }
 
-    /**
-     * @dataProvider constructDataProvider
-     */
+    #[DataProvider('constructDataProvider')]
     public function testConstructUsingIterable(array $values)
     {
         $this->assertToArray(array_reverse($values), new Stack(new \ArrayIterator($values)));
diff --git a/tests/Stack/_clone.php b/tests/Stack/_clone.php
index 5cc26ab..6f0b23d 100644
--- a/tests/Stack/_clone.php
+++ b/tests/Stack/_clone.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Stack;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _clone
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testClone($values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
 
         $clone = clone $instance;
 
diff --git a/tests/Stack/_echo.php b/tests/Stack/_echo.php
index fe6c0f0..dc8b65a 100644
--- a/tests/Stack/_echo.php
+++ b/tests/Stack/_echo.php
@@ -5,6 +5,6 @@ trait _echo
 {
     public function testEcho()
     {
-        $this->assertInstanceToString($this->getInstance());
+        $this->assertInstanceToString(static::getInstance());
     }
 }
diff --git a/tests/Stack/_empty.php b/tests/Stack/_empty.php
index 74de072..246b313 100644
--- a/tests/Stack/_empty.php
+++ b/tests/Stack/_empty.php
@@ -5,7 +5,7 @@ trait _empty
 {
     public function testArrayAccessEmpty()
     {
-        $set = $this->getInstance();
+        $set = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         empty($set['a']);
     }
diff --git a/tests/Stack/_foreach.php b/tests/Stack/_foreach.php
index f95cbb0..3869302 100644
--- a/tests/Stack/_foreach.php
+++ b/tests/Stack/_foreach.php
@@ -5,7 +5,7 @@ trait _foreach
 {
     public function testForEach()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->push('a');
         $instance->push('b');
diff --git a/tests/Stack/_isset.php b/tests/Stack/_isset.php
index d1d8c4c..2b4f5ee 100644
--- a/tests/Stack/_isset.php
+++ b/tests/Stack/_isset.php
@@ -5,7 +5,7 @@ trait _isset
 {
     public function testArrayAccessIsset()
     {
-        $set = $this->getInstance();
+        $set = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         isset($set['a']);
     }
diff --git a/tests/Stack/_jsonEncode.php b/tests/Stack/_jsonEncode.php
index 9e0803e..ab78353 100644
--- a/tests/Stack/_jsonEncode.php
+++ b/tests/Stack/_jsonEncode.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Stack;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _jsonEncode
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testJsonEncode(array $initial, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
         $this->assertEquals(json_encode($expected), json_encode($instance));
     }
 }
diff --git a/tests/Stack/_list.php b/tests/Stack/_list.php
index f649974..b6b12db 100644
--- a/tests/Stack/_list.php
+++ b/tests/Stack/_list.php
@@ -5,7 +5,7 @@ trait _list
 {
     public function testList()
     {
-        $instance = $this->getInstance(['a', 'b', 'c']);
+        $instance = static::getInstance(['a', 'b', 'c']);
         $this->expectListNotSupportedException();
         list($a, $b, $c) = $instance;
     }
diff --git a/tests/Stack/_serialize.php b/tests/Stack/_serialize.php
index a3300e0..c099bab 100644
--- a/tests/Stack/_serialize.php
+++ b/tests/Stack/_serialize.php
@@ -1,18 +1,18 @@
 <?php
 namespace Ds\Tests\Stack;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _serialize
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testSerialize(array $values, array $expected)
     {
         // Stack has to be serialized in push order, so that values can be
         // pushed when being unserialized.
         $expected = array_reverse($expected);
 
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertSerialized($expected, $instance, false);
     }
 }
diff --git a/tests/Stack/_unset.php b/tests/Stack/_unset.php
index 064ccbf..86d7ab2 100644
--- a/tests/Stack/_unset.php
+++ b/tests/Stack/_unset.php
@@ -5,7 +5,7 @@ trait _unset
 {
     public function testArrayAccessUnset()
     {
-        $set = $this->getInstance();
+        $set = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         unset($set['a']);
     }
diff --git a/tests/Stack/_var_dump.php b/tests/Stack/_var_dump.php
index 37fd500..48038dd 100644
--- a/tests/Stack/_var_dump.php
+++ b/tests/Stack/_var_dump.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Stack;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait _var_dump
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testVarDump(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertInstanceDump($expected, $instance);
     }
 }
diff --git a/tests/Stack/clear.php b/tests/Stack/clear.php
index 2d05be2..bee5191 100644
--- a/tests/Stack/clear.php
+++ b/tests/Stack/clear.php
@@ -5,7 +5,7 @@ trait clear
 {
     public function testClear()
     {
-        $instance = $this->getInstance($this->sample());
+        $instance = static::getInstance(self::sample());
         $instance->clear();
 
         $this->assertToArray([], $instance);
diff --git a/tests/Stack/copy.php b/tests/Stack/copy.php
index 27feaa1..25cc462 100644
--- a/tests/Stack/copy.php
+++ b/tests/Stack/copy.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Stack;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait copy
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testCopy(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $copy = $instance->copy();
 
         $this->assertEquals($instance->toArray(), $copy->toArray());
diff --git a/tests/Stack/count.php b/tests/Stack/count.php
index 5730a71..4d9f613 100644
--- a/tests/Stack/count.php
+++ b/tests/Stack/count.php
@@ -1,20 +1,20 @@
 <?php
 namespace Ds\Tests\Stack;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait count
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testCount(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertCount(count($expected), $instance);
     }
 
     public function testCountEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertCount(0, $instance);
     }
 }
diff --git a/tests/Stack/isEmpty.php b/tests/Stack/isEmpty.php
index 1933458..8bc1bd1 100644
--- a/tests/Stack/isEmpty.php
+++ b/tests/Stack/isEmpty.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Stack;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait isEmpty
 {
-    public function isEmptyDataProvider()
+    public static function isEmptyDataProvider()
     {
         // values, is empty
         return [
@@ -12,18 +14,16 @@ public function isEmptyDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider isEmptyDataProvider
-     */
+    #[DataProvider('isEmptyDataProvider')]
     public function testIsEmpty(array $values, bool $isEmpty)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertEquals($isEmpty, $instance->isEmpty());
     }
 
     public function testIsNotEmptyAfterPop()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertTrue($instance->isEmpty());
 
         $instance->push('a');
diff --git a/tests/Stack/peek.php b/tests/Stack/peek.php
index 7c6bffc..5f99e74 100644
--- a/tests/Stack/peek.php
+++ b/tests/Stack/peek.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Stack;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait peek
 {
-    public function peekDataProvider()
+    public static function peekDataProvider()
     {
         // initial, returned, expected result
         return [
@@ -12,12 +14,10 @@ public function peekDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider peekDataProvider
-     */
+    #[DataProvider('peekDataProvider')]
     public function testPeek($initial, $returned)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $value = $instance->peek();
 
@@ -27,7 +27,7 @@ public function testPeek($initial, $returned)
 
     public function testPeekNotAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->peek();
     }
diff --git a/tests/Stack/pop.php b/tests/Stack/pop.php
index 5fa1e2b..ff171b4 100644
--- a/tests/Stack/pop.php
+++ b/tests/Stack/pop.php
@@ -1,10 +1,12 @@
 <?php
 namespace Ds\Tests\Stack;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait pop
 {
 
-    public function popDataProvider()
+    public static function popDataProvider()
     {
         // initial, returned, expected result
         return [
@@ -13,12 +15,10 @@ public function popDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider popDataProvider
-     */
+    #[DataProvider('popDataProvider')]
     public function testPop($initial, $returned, array $expected)
     {
-        $instance = $this->getInstance($initial);
+        $instance = static::getInstance($initial);
 
         $result = $instance->pop();
 
@@ -29,7 +29,7 @@ public function testPop($initial, $returned, array $expected)
 
     public function testPopAll()
     {
-        $instance = $this->getInstance(range(1, self::MANY));
+        $instance = static::getInstance(range(1, self::MANY));
 
         while ( ! $instance->isEmpty()) {
             $instance->pop();
@@ -40,7 +40,7 @@ public function testPopAll()
 
     public function testPopNowAllowedWhenEmpty()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->expectEmptyNotAllowedException();
         $instance->pop();
     }
diff --git a/tests/Stack/push.php b/tests/Stack/push.php
index cb10910..93fcc1d 100644
--- a/tests/Stack/push.php
+++ b/tests/Stack/push.php
@@ -1,31 +1,29 @@
 <?php
 namespace Ds\Tests\Stack;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait push
 {
-    public function pushDataProvider()
+    public static function pushDataProvider()
     {
-        return $this->basicDataProvider();
+        return self::basicDataProvider();
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testPushVariadic(array $values, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->push(...$values);
 
         $this->assertToArray($expected, $instance);
         $this->assertCount(count($expected), $instance);
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testPush(array $values, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($values as $value) {
             $instance->push($value);
@@ -35,12 +33,10 @@ public function testPush(array $values, array $expected)
         $this->assertCount(count($expected), $instance);
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testArrayAccessPush(array $values, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($values as $value) {
             $instance[] = $value;
@@ -50,12 +46,10 @@ public function testArrayAccessPush(array $values, array $expected)
         $this->assertCount(count($expected), $instance);
     }
 
-    /**
-     * @dataProvider pushDataProvider
-     */
+    #[DataProvider('pushDataProvider')]
     public function testArrayAccessPushByMethod(array $values, array $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         foreach ($values as $value) {
             $instance->offsetSet(null, $value);
@@ -67,7 +61,7 @@ public function testArrayAccessPushByMethod(array $values, array $expected)
 
     public function testPushCircularReference()
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $instance->push($instance);
         $this->assertToArray([$instance], $instance);
     }
diff --git a/tests/Stack/toArray.php b/tests/Stack/toArray.php
index fd3a883..ffaafbd 100644
--- a/tests/Stack/toArray.php
+++ b/tests/Stack/toArray.php
@@ -1,14 +1,14 @@
 <?php
 namespace Ds\Tests\Stack;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait toArray
 {
-    /**
-     * @dataProvider basicDataProvider
-     */
+    #[DataProvider('basicDataProvider')]
     public function testToArray(array $values, array $expected)
     {
-        $instance = $this->getInstance($values);
+        $instance = static::getInstance($values);
         $this->assertToArray($expected, $instance);
     }
 }
diff --git a/tests/StackTest.php b/tests/StackTest.php
index 3f8e582..5636460 100644
--- a/tests/StackTest.php
+++ b/tests/StackTest.php
@@ -4,7 +4,7 @@
 use ArrayAccess;
 use Ds\Collection;
 
-class StackTest extends CollectionTest
+class StackTest extends CollectionTestCase
 {
     use Stack\__construct;
     use Stack\_clone;
@@ -30,12 +30,12 @@ class StackTest extends CollectionTest
     use Stack\push;
     use Stack\toArray;
 
-    public function getInstance(array $values = [])
+    public static function getInstance(array $values = [])
     {
         return new \Ds\Stack($values);
     }
 
-    public function basicDataProvider()
+    public static function basicDataProvider()
     {
         // Stack should produce values in reverse order.
         return array_map(function($data) {
@@ -52,13 +52,13 @@ public function serializeDataProvider()
 
     public function testArrayAccessSet()
     {
-        $set = $this->getInstance();
+        $set = static::getInstance();
         $this->expectArrayAccessUnsupportedException();
         $set['a'] = 1;
     }
 
     public function testImplementsArrayAccess()
     {
-        $this->assertInstanceOf(ArrayAccess::class, $this->getInstance());
+        $this->assertInstanceOf(ArrayAccess::class, static::getInstance());
     }
 }
diff --git a/tests/Vector/__construct.php b/tests/Vector/__construct.php
index 33c9e8d..17c76d2 100644
--- a/tests/Vector/__construct.php
+++ b/tests/Vector/__construct.php
@@ -1,33 +1,31 @@
 <?php
 namespace Ds\Tests\Vector;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 use Ds\Vector;
 
 trait __construct
 {
-    public function constructDataProvider()
+    public static function constructDataProvider()
     {
         return array_map(function($a) { return [$a, $a]; }, [
             [],
             ['a'],
             ['a', 'b'],
             ['a', 'b', 'c'],
-            $this->sample(),
+            self::sample(),
             range(1, self::MANY),
         ]);
     }
 
-    /**
-     * @dataProvider constructDataProvider
-     */
+    #[DataProvider('constructDataProvider')]
     public function testConstruct($values, array $expected)
     {
         $this->assertToArray($expected, new Vector($values));
     }
 
-   /**
-     * @dataProvider constructDataProvider
-     */
+   #[DataProvider('constructDataProvider')]
     public function testConstructUsingNonArrayIterable(array $values, array $expected)
     {
         $this->assertToArray($expected, new Vector(new \ArrayIterator($values)));
diff --git a/tests/Vector/allocate.php b/tests/Vector/allocate.php
index 0cc525f..1072101 100644
--- a/tests/Vector/allocate.php
+++ b/tests/Vector/allocate.php
@@ -1,9 +1,11 @@
 <?php
 namespace Ds\Tests\Vector;
 
+use PHPUnit\Framework\Attributes\DataProvider;
+
 trait allocate
 {
-    public function allocateDataProvider()
+    public static function allocateDataProvider()
     {
         $m = \Ds\Vector::MIN_CAPACITY;
 
@@ -22,12 +24,10 @@ public function allocateDataProvider()
         ];
     }
 
-    /**
-     * @dataProvider allocateDataProvider
-     */
+    #[DataProvider('allocateDataProvider')]
     public function testAllocate(int $initial, int $allocate, int $expected)
     {
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
 
         $instance->allocate($initial);
         $instance->allocate($allocate);
diff --git a/tests/Vector/capacity.php b/tests/Vector/capacity.php
index ff710f8..6dc41b6 100644
--- a/tests/Vector/capacity.php
+++ b/tests/Vector/capacity.php
@@ -7,7 +7,7 @@ public function testCapacity()
     {
         $min = \Ds\Vector::MIN_CAPACITY;
 
-        $instance = $this->getInstance();
+        $instance = static::getInstance();
         $this->assertEquals($min, $instance->capacity());
 
         for ($i = 0; $i < $min; $i++) {
@@ -42,7 +42,7 @@ public function testAutoTruncate()
             0  =>   8,
         ];
 
-        $instance = $this->getInstance(range(1, array_keys($boundaries)[0]));
+        $instance = static::getInstance(range(1, array_keys($boundaries)[0]));
 
         for (;;) {
             if ( ! is_null(($expected = $boundaries[$instance->count()] ?? null))) {
@@ -61,7 +61,7 @@ public function testClearResetsCapacity()
     {
         $min = \Ds\Vector::MIN_CAPACITY;
 
-        $instance = $this->getInstance(range(1, self::MANY));
+        $instance = static::getInstance(range(1, self::MANY));
         $instance->clear();
         $this->assertEquals($min, $instance->capacity());
     }
diff --git a/tests/VectorTest.php b/tests/VectorTest.php
index 7290be0..1a8fe6e 100644
--- a/tests/VectorTest.php
+++ b/tests/VectorTest.php
@@ -3,7 +3,7 @@
 
 use ArrayAccess;
 
-class VectorTest extends CollectionTest
+class VectorTest extends CollectionTestCase
 {
     use Sequence\_clone;
     use Sequence\_echo;
@@ -51,13 +51,13 @@ class VectorTest extends CollectionTest
     use Sequence\toArray;
     use Sequence\unshift;
 
-    public function getInstance(array $values = [])
+    public static function getInstance(array $values = [])
     {
         return new \Ds\Vector($values);
     }
 
     public function testImplementsArrayAccess()
     {
-        $this->assertInstanceOf(ArrayAccess::class, $this->getInstance());
+        $this->assertInstanceOf(ArrayAccess::class, static::getInstance());
     }
 }