diff --git a/CommonLogic/Contexts/Scopes/SessionContextScope.php b/CommonLogic/Contexts/Scopes/SessionContextScope.php
index e4b44ba36..169e01030 100644
--- a/CommonLogic/Contexts/Scopes/SessionContextScope.php
+++ b/CommonLogic/Contexts/Scopes/SessionContextScope.php
@@ -219,12 +219,10 @@ protected function sessionClose()
      */
     protected function sessionIsOpen()
     {
-        if (php_sapi_name() !== 'cli') {
-            if (version_compare(phpversion(), '5.4.0', '>=')) {
-                return session_status() === PHP_SESSION_ACTIVE ? TRUE : FALSE;
-            } else {
-                return session_id() === '' ? FALSE : TRUE;
-            }
+        if (version_compare(phpversion(), '5.4.0', '>=')) {
+            return session_status() === PHP_SESSION_ACTIVE ? TRUE : FALSE;
+        } else {
+            return session_id() === '' ? FALSE : TRUE;
         }
         return FALSE;
     }
@@ -236,7 +234,11 @@ protected function sessionIsOpen()
      */
     protected function getSessionContextData()
     {
-        return $_SESSION['exface']['contexts'];
+        if (isset($_SESSION['exface']) && isset($_SESSION['exface']['contexts'])) {
+            return $_SESSION['exface']['contexts'];
+        } else {
+            return null;
+        }
     }
 
     /**
@@ -259,7 +261,12 @@ protected function setSessionContextData($key, $value)
      */
     protected function getSessionData(string $key)
     {
-        return $_SESSION['exface'][$key];
+        
+        if (isset($_SESSION['exface']) && isset($_SESSION['exface'][$key])) {
+            return $_SESSION['exface'][$key];
+        } else {
+            return null;
+        }
     }
     
     /**
diff --git a/CommonLogic/Filemanager.php b/CommonLogic/Filemanager.php
index bfb34e3fe..842292925 100644
--- a/CommonLogic/Filemanager.php
+++ b/CommonLogic/Filemanager.php
@@ -33,6 +33,8 @@ class Filemanager extends Filesystem implements WorkbenchDependantInterface
 
     private $path_to_config_folder = null;
 
+    private $path_to_translations_folder = null;
+
     private $path_to_user_data_folder = null;
 
     private $path_to_backup_folder = null;
diff --git a/codeception.yml b/codeception.yml
new file mode 100644
index 000000000..4d7027a97
--- /dev/null
+++ b/codeception.yml
@@ -0,0 +1,12 @@
+paths:
+    tests: tests
+    output: tests/_output
+    data: tests/_data
+    support: tests/_support
+    envs: tests/_envs
+actor_suffix: Tester
+extensions:
+    enabled:
+        - Codeception\Extension\RunFailed
+settings:
+    bootstrap: _bootstrap.php
diff --git a/composer.json b/composer.json
index 81577e38b..e4db5e0ff 100644
--- a/composer.json
+++ b/composer.json
@@ -40,6 +40,9 @@
         "kabachello/fileroute": "~0.2",
         "guzzlehttp/guzzle": "^6.2.2"
     },
+	"require-dev": {
+		"codeception/codeception": "^2.3"
+	},
     "suggest": {
         "npm-asset/workbox-sw": "Allows templates to use the tools from the AbstractServiceWorkerTemplate"
     },
diff --git a/tests/_data/.gitkeep b/tests/_data/.gitkeep
new file mode 100644
index 000000000..e69de29bb
diff --git a/tests/_output/.gitignore b/tests/_output/.gitignore
new file mode 100644
index 000000000..c96a04f00
--- /dev/null
+++ b/tests/_output/.gitignore
@@ -0,0 +1,2 @@
+*
+!.gitignore
\ No newline at end of file
diff --git a/tests/_support/AcceptanceTester.php b/tests/_support/AcceptanceTester.php
new file mode 100644
index 000000000..4c7dcbb6d
--- /dev/null
+++ b/tests/_support/AcceptanceTester.php
@@ -0,0 +1,26 @@
+<?php
+
+
+/**
+ * Inherited Methods
+ * @method void wantToTest($text)
+ * @method void wantTo($text)
+ * @method void execute($callable)
+ * @method void expectTo($prediction)
+ * @method void expect($prediction)
+ * @method void amGoingTo($argumentation)
+ * @method void am($role)
+ * @method void lookForwardTo($achieveValue)
+ * @method void comment($description)
+ * @method \Codeception\Lib\Friend haveFriend($name, $actorClass = NULL)
+ *
+ * @SuppressWarnings(PHPMD)
+*/
+class AcceptanceTester extends \Codeception\Actor
+{
+    use _generated\AcceptanceTesterActions;
+
+   /**
+    * Define custom actions here
+    */
+}
diff --git a/tests/_support/FunctionalTester.php b/tests/_support/FunctionalTester.php
new file mode 100644
index 000000000..7e888f8b2
--- /dev/null
+++ b/tests/_support/FunctionalTester.php
@@ -0,0 +1,26 @@
+<?php
+
+
+/**
+ * Inherited Methods
+ * @method void wantToTest($text)
+ * @method void wantTo($text)
+ * @method void execute($callable)
+ * @method void expectTo($prediction)
+ * @method void expect($prediction)
+ * @method void amGoingTo($argumentation)
+ * @method void am($role)
+ * @method void lookForwardTo($achieveValue)
+ * @method void comment($description)
+ * @method \Codeception\Lib\Friend haveFriend($name, $actorClass = NULL)
+ *
+ * @SuppressWarnings(PHPMD)
+*/
+class FunctionalTester extends \Codeception\Actor
+{
+    use _generated\FunctionalTesterActions;
+
+   /**
+    * Define custom actions here
+    */
+}
diff --git a/tests/_support/Helper/Acceptance.php b/tests/_support/Helper/Acceptance.php
new file mode 100644
index 000000000..65b94215e
--- /dev/null
+++ b/tests/_support/Helper/Acceptance.php
@@ -0,0 +1,10 @@
+<?php
+namespace Helper;
+
+// here you can define custom actions
+// all public methods declared in helper class will be available in $I
+
+class Acceptance extends \Codeception\Module
+{
+
+}
diff --git a/tests/_support/Helper/Functional.php b/tests/_support/Helper/Functional.php
new file mode 100644
index 000000000..4183cb0a5
--- /dev/null
+++ b/tests/_support/Helper/Functional.php
@@ -0,0 +1,10 @@
+<?php
+namespace Helper;
+
+// here you can define custom actions
+// all public methods declared in helper class will be available in $I
+
+class Functional extends \Codeception\Module
+{
+
+}
diff --git a/tests/_support/Helper/Unit.php b/tests/_support/Helper/Unit.php
new file mode 100644
index 000000000..6064d3732
--- /dev/null
+++ b/tests/_support/Helper/Unit.php
@@ -0,0 +1,10 @@
+<?php
+namespace Helper;
+
+// here you can define custom actions
+// all public methods declared in helper class will be available in $I
+
+class Unit extends \Codeception\Module
+{
+
+}
diff --git a/tests/_support/UnitTester.php b/tests/_support/UnitTester.php
new file mode 100644
index 000000000..28353572c
--- /dev/null
+++ b/tests/_support/UnitTester.php
@@ -0,0 +1,26 @@
+<?php
+
+
+/**
+ * Inherited Methods
+ * @method void wantToTest($text)
+ * @method void wantTo($text)
+ * @method void execute($callable)
+ * @method void expectTo($prediction)
+ * @method void expect($prediction)
+ * @method void amGoingTo($argumentation)
+ * @method void am($role)
+ * @method void lookForwardTo($achieveValue)
+ * @method void comment($description)
+ * @method \Codeception\Lib\Friend haveFriend($name, $actorClass = NULL)
+ *
+ * @SuppressWarnings(PHPMD)
+*/
+class UnitTester extends \Codeception\Actor
+{
+    use _generated\UnitTesterActions;
+
+   /**
+    * Define custom actions here
+    */
+}
diff --git a/tests/_support/_generated/.gitignore b/tests/_support/_generated/.gitignore
new file mode 100644
index 000000000..c96a04f00
--- /dev/null
+++ b/tests/_support/_generated/.gitignore
@@ -0,0 +1,2 @@
+*
+!.gitignore
\ No newline at end of file
diff --git a/tests/acceptance.suite.yml b/tests/acceptance.suite.yml
new file mode 100644
index 000000000..bb977c486
--- /dev/null
+++ b/tests/acceptance.suite.yml
@@ -0,0 +1,12 @@
+# Codeception Test Suite Configuration
+#
+# Suite for acceptance tests.
+# Perform tests in browser using the WebDriver or PhpBrowser.
+# If you need both WebDriver and PHPBrowser tests - create a separate suite.
+
+actor: AcceptanceTester
+modules:
+    enabled:
+        - PhpBrowser:
+            url: http://localhost/myapp
+        - \Helper\Acceptance
\ No newline at end of file
diff --git a/tests/functional.suite.yml b/tests/functional.suite.yml
new file mode 100644
index 000000000..94c1fe29b
--- /dev/null
+++ b/tests/functional.suite.yml
@@ -0,0 +1,12 @@
+# Codeception Test Suite Configuration
+#
+# Suite for functional tests
+# Emulate web requests and make application process them
+# Include one of framework modules (Symfony2, Yii2, Laravel5) to use it
+# Remove this suite if you don't use frameworks
+
+actor: FunctionalTester
+modules:
+    enabled:
+        # add a framework module here
+        - \Helper\Functional
\ No newline at end of file
diff --git a/tests/unit.suite.yml b/tests/unit.suite.yml
new file mode 100644
index 000000000..026c91db9
--- /dev/null
+++ b/tests/unit.suite.yml
@@ -0,0 +1,9 @@
+# Codeception Test Suite Configuration
+#
+# Suite for unit or integration tests.
+
+actor: UnitTester
+modules:
+    enabled:
+        - Asserts
+        - \Helper\Unit
\ No newline at end of file
diff --git a/tests/unit/DateTest.php b/tests/unit/DateTest.php
new file mode 100644
index 000000000..6549d87dd
--- /dev/null
+++ b/tests/unit/DateTest.php
@@ -0,0 +1,60 @@
+<?php
+use exface\Core\Formulas\Date;
+use exface\Core\CommonLogic\Selectors\FormulaSelector;
+
+class DateTest extends \Codeception\Test\Unit
+{
+
+    private $date;
+
+    const TEST_DATE = '2018-01-11';
+
+    const TEST_FORMAT = 'd.m.Y';
+
+    protected function _before()
+    {
+        global $exface;
+        $this->date = new Date(new FormulaSelector($exface, 'exface.Core.Date'));
+    }
+
+    protected function _after()
+    {
+        $this->date = null;
+    }
+
+    public function testFormatDate()
+    {
+        $formattedDate = $this->date->formatDate(self::TEST_DATE, self::TEST_FORMAT);
+        $this->assertEquals('11.01.2018', $formattedDate);
+    }
+
+    public function testFormatDateFromEmptyFormat()
+    {
+        $formattedDate = $this->date->formatDate(self::TEST_DATE, '');
+        $this->assertEquals('11.01.2018', $formattedDate);
+        
+        $formattedDate = $this->date->formatDate(self::TEST_DATE, null);
+        $this->assertEquals('11.01.2018', $formattedDate);
+    }
+
+    public function testFormatDateFromEmptyDate()
+    {
+        $formattedDate = $this->date->formatDate('', self::TEST_FORMAT);
+        $this->assertEquals((new DateTime())->format(self::TEST_FORMAT), $formattedDate);
+        
+        $formattedDate = $this->date->formatDate(null, self::TEST_FORMAT);
+        $this->assertEquals((new DateTime())->format(self::TEST_FORMAT), $formattedDate);
+    }
+
+    public function testFormatDateFromInvalidDate()
+    {
+        $formattedDate = $this->date->formatDate('2018-13-12', self::TEST_FORMAT);
+        $this->assertEquals('2018-13-12', $formattedDate);
+    }
+
+    public function testRun()
+    {
+        $formattedDate = $this->date->run(self::TEST_DATE, self::TEST_FORMAT);
+        $this->assertEquals('11.01.2018', $formattedDate);
+    }
+}
\ No newline at end of file
diff --git a/tests/unit/_bootstrap.php b/tests/unit/_bootstrap.php
new file mode 100644
index 000000000..975858741
--- /dev/null
+++ b/tests/unit/_bootstrap.php
@@ -0,0 +1,7 @@
+<?php
+
+global $exface;
+if (! $exface) {
+    $exface = new exface\Core\CommonLogic\Workbench();
+    $exface->start();
+}