Add test class JUnit5TestFinderJupiterTest

The class contains some tests that cover the current capabilities of
JUnit5TestFinder and it was missing from the tests.
This class does NOT resemble the other 2 existing classes:
JUnit3TestFinder and JUnit4TestFinder

org.eclipse.jdt.ui.tests/META-INF/MANIFEST.MF

@@ -78,7 +78,8 @@ Require-Bundle:
 Bundle-RequiredExecutionEnvironment: JavaSE-17
 Eclipse-BundleShape: dir
 Bundle-ActivationPolicy: lazy
-Import-Package: org.junit.jupiter.api,
+Import-Package: org.assertj.core.api;version="3.24.2",
+ org.junit.jupiter.api,
  org.junit.platform.suite.api,
  org.junit.platform.suite.commons;status=INTERNAL,
  org.junit.platform.suite.engine;status=INTERNAL

org.eclipse.jdt.ui.tests/testresources/testClasses/JupiterTests.java

@@ -0,0 +1,76 @@
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestTemplate;
+
+import junit.framework.TestCase;
+
+/**
+ * This class contains some internal classes that should be found/not found by the
+ * JUnit5TestFinder.<br/>
+ * <br/>
+ * The names of the classes give a hint about whether or not the class should be found and the
+ * reason for that. In order to be discovered, a class needs to fulfill these requirements:
+ * <ul>
+ * <li>It should be visible (it can <strong>not</strong> be <code>private</code>)</li>
+ * <li>It must have tests in it.</li>
+ * </ul>
+ *
+ * Whether or not the class can be instantiated (<i>i.e.</i> if they have a non-private empty
+ * constructor) does not play a role in the discoverability, but running tests on that class will
+ * throw an exception,
+ */
+class JupiterTests {
+	/**
+	 * Methods using this annotation are also considered tests
+	 */
+	@Test
+	@Retention(RetentionPolicy.RUNTIME)
+	@interface CustomTestAnnotation {}
+
+	static class FoundStatic {
+		@Test void myTest() {}
+	}
+
+	static class FoundStaticCustomTestAnnotation {
+		@CustomTestAnnotation void myTest() {}
+	}
+
+	private static class NotFoundPrivate {
+		@CustomTestAnnotation void myTest() {}
+	}
+
+	static class NotFoundHasNoTests {}
+
+	static class FoundExtendsTestCase extends TestCase {
+		@Test void myTest() {}
+	}
+
+	static class FoundExtendsTestCaseCustomTestAnnotation extends TestCase {
+		@CustomTestAnnotation public void myTest() {}
+	}
+
+	private static class NotFoundPrivateExtendsTestCase extends TestCase {
+		@Test public void myTest() {}
+	}
+
+	static class FoundTestTemplateClass {
+		@TestTemplate void myTestTemplate() {}
+	}
+
+	static abstract class NotFoundAbstractWithInnerClass {
+		class NotFoundInnerInstanceClassWithTest {
+			@Test void myTest() {}
+		}
+	}
+
+	static class NotFoundExtendsAbstractWithInnerWithTest extends NotFoundAbstractWithInnerClass {}
+
+	static class FoundHasInnerClassWithNested {
+		@Nested class FoundExtendsAbstractWithNested extends NotFoundAbstractWithInnerClass {
+			@Test void myTest() {}
+		}
+	}
+}

org.eclipse.jdt.ui.tests/ui/org/eclipse/jdt/junit/tests/JUnit5TestFinderJupiterTest.java

@@ -0,0 +1,144 @@
+/*******************************************************************************
+ * Copyright (c) 2023 Vector Informatik GmbH and others.
+ *
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Vector Informatik GmbH - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.jdt.junit.tests;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameter;
+import org.junit.runners.Parameterized.Parameters;
+
+import org.eclipse.jdt.junit.JUnitCore;
+import org.eclipse.jdt.testplugin.JavaProjectHelper;
+
+import org.eclipse.jdt.core.IClasspathEntry;
+import org.eclipse.jdt.core.ICompilationUnit;
+import org.eclipse.jdt.core.IJavaProject;
+import org.eclipse.jdt.core.IPackageFragment;
+import org.eclipse.jdt.core.IPackageFragmentRoot;
+import org.eclipse.jdt.core.IType;
+import org.eclipse.jdt.core.JavaCore;
+import org.eclipse.jdt.core.JavaModelException;
+
+import org.eclipse.jdt.internal.junit.launcher.JUnit5TestFinder;
+
+
+/**
+ * Test if the <code>JUnit5TestFinder</code> can find tests annotated with the API of JUnit5
+ * (Jupiter)
+ */
+@RunWith(Parameterized.class)
+public class JUnit5TestFinderJupiterTest {
+
+	record TestScenario(String testClass, int testTypesCount) {
+	}
+
+	private static final String JAVA_CLASS_NAME= "JupiterTests";
+
+	private static final String JAVA_FILE_NAME= JAVA_CLASS_NAME + ".java";
+
+	private static final Path TEST_CLASS_FILE= Path.of("testresources").resolve("testClasses").resolve(JAVA_FILE_NAME);
+
+	private static IJavaProject javaProject;
+
+	@Parameters(name= "{0}")
+	public static Collection<TestScenario> getCompilationUnits() {
+
+		// These are the current "valid" results
+		return List.of(new TestScenario(JAVA_CLASS_NAME, 7), //
+				new TestScenario("CustomTestAnnotation", 0), // Not a test class
+				new TestScenario("FoundStatic", 1), //
+				new TestScenario("FoundStaticCustomTestAnnotation", 1), //
+				new TestScenario("NotFoundPrivate", 0), // private class
+				new TestScenario("NotFoundHasNoTests", 0), // empty class (no tests)
+				new TestScenario("FoundExtendsTestCase", 1), //
+				new TestScenario("FoundExtendsTestCaseCustomTestAnnotation", 1), //
+				new TestScenario("NotFoundPrivateExtendsTestCase", 0), // private class
+				new TestScenario("FoundTestTemplateClass", 1), //
+				new TestScenario("NotFoundAbstractWithInnerClass", 0), // can't be instantiated
+				new TestScenario("NotFoundExtendsAbstractWithInnerWithTest", 0), // FIXME: why isn't this one found even though it can be instantiated?
+				new TestScenario("FoundHasInnerClassWithNested", 1), //
+				new TestScenario("NotFoundInnerInstanceClassWithTest", 0), // has test but it can't be instantiated (needs enclosing instance)
+				new TestScenario("FoundExtendsAbstractWithNested", 1) //
+		);
+
+	}
+
+	@Parameter
+	public TestScenario scenario;
+
+	private static ICompilationUnit compilationUnit;
+
+	@BeforeClass
+	public static void beforeClass() throws Exception {
+		javaProject= JavaProjectHelper.createJavaProject("TestProject", "bin");
+		JavaProjectHelper.addRTJar(javaProject);
+		IClasspathEntry cpe= JavaCore.newContainerEntry(JUnitCore.JUNIT5_CONTAINER_PATH);
+		JavaProjectHelper.addToClasspath(javaProject, cpe);
+		JavaProjectHelper.set18CompilerOptions(javaProject);
+
+		IPackageFragmentRoot root= JavaProjectHelper.addSourceContainer(javaProject, "src");
+		IPackageFragment packageFragment= root.createPackageFragment("somepackage", true, null);
+
+		compilationUnit= createCompilationUnit(packageFragment);
+	}
+
+	@AfterClass
+	public static void afterClass() throws Exception {
+		JavaProjectHelper.delete(javaProject);
+	}
+
+	@Test
+	public void testFindTestsInContainer() throws Exception {
+		IType type= findTypeWithName(scenario.testClass());
+		Set<IType> foundTestTypes= new HashSet<>();
+
+		JUnit5TestFinder objectUnderTest= new JUnit5TestFinder();
+		objectUnderTest.findTestsInContainer(type, foundTestTypes, null);
+
+		assertThat(foundTestTypes).hasSize(scenario.testTypesCount());
+	}
+
+
+	private IType findTypeWithName(String name) throws JavaModelException {
+		for (IType type : compilationUnit.getAllTypes()) {
+			if (type.getElementName().equals(name))
+				return type;
+		}
+		return null;
+	}
+
+	private static ICompilationUnit createCompilationUnit(IPackageFragment packageFragment) throws IOException {
+		String content= Files.readString(TEST_CLASS_FILE);
+
+		try {
+			return packageFragment.createCompilationUnit(JAVA_FILE_NAME, content, false, null);
+		} catch (JavaModelException e) {
+			// let the test fail
+			throw new RuntimeException(e);
+		}
+	}
+}

org.eclipse.jdt.ui.tests/ui/org/eclipse/jdt/junit/tests/JUnitJUnitTests.java

@@ -41,6 +41,7 @@
 JUnit3TestFinderTest.class,
 JUnit4TestFinderTest.class,
 JUnit4TestFinderTest16.class,
+JUnit5TestFinderJupiterTest.class,
 
 TestSorting.class
 /**