adding java integ test

build.gradle

@@ -1,3 +1,5 @@
+import org.opensearch.gradle.test.RestIntegTestTask
+
 apply plugin: 'java'
 apply plugin: 'idea'
 apply plugin: 'opensearch.opensearchplugin'
@@ -12,20 +14,29 @@ opensearchplugin {
 }
 
 
-// disabling some unnecessary validations for this plugin
+// Allow test cases to be named Tests without having to be inherited from LuceneTestCase.
+// see https://github.com/elastic/elasticsearch/blob/323f312bbc829a63056a79ebe45adced5099f6e6/buildSrc/src/main/java/org/elasticsearch/gradle/precommit/TestingConventionsTasks.java
 testingConventions.enabled = false
+
+licenseHeaders.enabled = true
+dependencyLicenses.enabled = false
+thirdPartyAudit.enabled = false
 loggerUsageCheck.enabled = false
-validateNebulaPom.enabled = false
 
 buildscript {
+    ext {
+        opensearch_group = "org.opensearch"
+        opensearch_version = System.getProperty("opensearch.version", "1.0.0-beta1")
+    }
+
     repositories {
         mavenCentral()
         jcenter()
         mavenLocal()
     }
 
     dependencies {
-        classpath "org.opensearch.gradle:build-tools:1.0.0-beta1"
+        classpath "${opensearch_group}.gradle:build-tools:${opensearch_version}"
     }
 }
 
@@ -37,3 +48,67 @@ dependencies {
     // required for the yaml test to run
     yamlRestTestImplementation 'org.apache.logging.log4j:log4j-core:2.11.1'
 }
+
+test {
+    include '**/*Tests.class'
+    systemProperty 'tests.security.manager', 'false'
+}
+
+// See package README.md for details on using these tasks.
+def _numNodes = findProperty('numNodes') as Integer ?: 1
+
+task integTest(type: RestIntegTestTask) {
+    description = "Run tests against a cluster"
+    testClassesDirs = sourceSets.test.output.classesDirs
+    classpath = sourceSets.test.runtimeClasspath
+}
+tasks.named("check").configure { dependsOn(integTest) }
+
+integTest {
+    // The 'doFirst' delays till execution time.
+    doFirst {
+        // Tell the test JVM if the cluster JVM is running under a debugger so that tests can
+        // use longer timeouts for requests.
+        def isDebuggingCluster = getDebug() || System.getProperty("test.debug") != null
+        systemProperty 'cluster.debug', isDebuggingCluster
+        // Set number of nodes system property to be used in tests
+        systemProperty 'cluster.number_of_nodes', "${_numNodes}"
+        // There seems to be an issue when running multi node run or integ tasks with unicast_hosts
+        // not being written, the waitForAllConditions ensures it's written
+        getClusters().forEach { cluster ->
+            cluster.waitForAllConditions()
+        }
+    }
+
+    // The --debug-jvm command-line option makes the cluster debuggable; this makes the tests debuggable
+    if (System.getProperty("test.debug") != null) {
+        jvmArgs '-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=*:5005'
+    }
+}
+
+testClusters.integTest {
+    testDistribution = "INTEG_TEST"
+    // When running integration tests it doesn't forward the --debug-jvm to the cluster anymore
+    // i.e. we have to use a custom property to flag when we want to debug elasticsearch JVM
+    // since we also support multi node integration tests we increase debugPort per node
+    if (System.getProperty("opensearch.debug") != null) {
+        def debugPort = 5005
+        nodes.forEach { node ->
+            node.jvmArgs("-agentlib:jdwp=transport=dt_socket,server=n,suspend=y,address=*:${debugPort}")
+            debugPort += 1
+        }
+    }
+    plugin(project.tasks.bundlePlugin.archiveFile)
+}
+
+run {
+    doFirst {
+        // There seems to be an issue when running multi node run or integ tasks with unicast_hosts
+        // not being written, the waitForAllConditions ensures it's written
+        getClusters().forEach { cluster ->
+            cluster.waitForAllConditions()
+        }
+    }
+
+    useCluster testClusters.integTest
+}

src/test/java/org/opensearch/rest/action/HelloWorldPluginIT.java

@@ -0,0 +1,67 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+
+package org.opensearch.rest.action;
+
+import com.carrotsearch.randomizedtesting.annotations.ThreadLeakScope;
+import org.apache.http.entity.ContentType;
+import org.apache.http.nio.entity.NStringEntity;
+import org.apache.http.util.EntityUtils;
+import org.opensearch.client.Request;
+import org.opensearch.client.Response;
+import org.opensearch.plugins.Plugin;
+import org.opensearch.test.OpenSearchIntegTestCase;
+
+import java.io.IOException;
+import java.util.Collection;
+import java.util.Collections;
+
+import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.equalTo;
+
+@ThreadLeakScope(ThreadLeakScope.Scope.NONE)
+@OpenSearchIntegTestCase.ClusterScope(scope = OpenSearchIntegTestCase.Scope.SUITE)
+public class HelloWorldPluginIT extends OpenSearchIntegTestCase {
+
+    @Override
+    protected Collection<Class<? extends Plugin>> nodePlugins() {
+        return Collections.singletonList(HelloWorldPlugin.class);
+    }
+
+    public void testPluginInstalled() throws IOException {
+        Response response = createRestClient().performRequest(new Request("GET", "/_cat/plugins"));
+        String body = EntityUtils.toString(response.getEntity());
+
+        logger.info("response body: {}", body);
+        assertThat(body, containsString("my-rest-plugin"));
+    }
+
+    public void testPluginIsWorkingNoValue() throws IOException {
+        Response response = createRestClient().performRequest(new Request("GET", "/hello-world"));
+        String body = EntityUtils.toString(response.getEntity());
+
+        logger.info("response body: {}", body);
+        assertThat(body, equalTo("Hi! Your plugin is installed and working:)"));
+    }
+
+    public void testPluginIsWorkingWithValue() throws IOException {
+        Request request = new Request("POST", "/hello-world");
+        request.setEntity(
+                new NStringEntity(
+                        "{\"name\":\"Amitai\"}",
+                        ContentType.APPLICATION_JSON
+                )
+        );
+        Response response = createRestClient().performRequest(request);
+        String body = EntityUtils.toString(response.getEntity());
+
+        logger.info("response body: {}", body);
+        assertThat(body, equalTo("Hi Amitai! Your plugin is installed and working:)"));
+    }
+}