#40: Do not discover plain classes without tests

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junit-tests/src/test/java/org/junit/gen5/engine/junit4/JUnit4TestEngineClassSpecificationResolutionTests.java

@@ -145,6 +145,16 @@ void resolvesJUnit3Suites() {
 		assertThat(testMethodDescriptor.getChildren()).isEmpty();
 	}
 
+	@Test
+	void doesNotResolvePlainOldJavaClassesWithoutAnyTest() {
+		Class<?> testClass = PlainOldJavaClassWithoutAnyTest.class;
+		TestPlanSpecification specification = build(forClass(testClass));
+
+		TestDescriptor engineDescriptor = engine.discoverTests(specification);
+
+		assertThat(engineDescriptor.getChildren()).isEmpty();
+	}
+
 	public static class PlainJUnit4TestCaseWithSingleTestWhichFails {
 
 		@org.junit.Test
@@ -192,6 +202,14 @@ public static junit.framework.Test suite() {
 
 	}
 
+	public static class PlainOldJavaClassWithoutAnyTest {
+
+		public void doSomething() {
+			// no-op
+		}
+
+	}
+
 	private static <T> T getOnlyElement(Iterable<T> iterable) {
 		Iterator<T> iterator = iterable.iterator();
 		Preconditions.condition(iterator.hasNext(), () -> "iterable must not be empty: " + iterable);

junit4-engine/src/main/java/org/junit/gen5/engine/junit4/discovery/DefensiveAllDefaultPossibilitiesBuilder.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2015-2016 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v1.0 which
+ * accompanies this distribution and is available at
+ *
+ * http://www.eclipse.org/legal/epl-v10.html
+ */
+
+package org.junit.gen5.engine.junit4.discovery;
+
+import java.lang.reflect.Method;
+import java.util.List;
+import java.util.function.Predicate;
+
+import org.junit.gen5.commons.util.ReflectionUtils;
+import org.junit.internal.builders.AllDefaultPossibilitiesBuilder;
+import org.junit.internal.builders.JUnit4Builder;
+import org.junit.runner.Runner;
+
+class DefensiveAllDefaultPossibilitiesBuilder extends AllDefaultPossibilitiesBuilder {
+
+	private final DefensiveJUnit4Builder defensiveJUnit4Builder = new DefensiveJUnit4Builder();
+
+	DefensiveAllDefaultPossibilitiesBuilder() {
+		super(true);
+	}
+
+	@Override
+	protected JUnit4Builder junit4Builder() {
+		return defensiveJUnit4Builder;
+	}
+
+	private static class DefensiveJUnit4Builder extends JUnit4Builder {
+
+		private final Predicate<Method> hasTestAnnotation = new IsPotentialJUnit4TestMethod();
+
+		@Override
+		public Runner runnerForClass(Class<?> testClass) throws Throwable {
+			if (containsTestMethods(testClass)) {
+				return super.runnerForClass(testClass);
+			}
+			return null;
+		}
+
+		private boolean containsTestMethods(Class<?> testClass) {
+			List<Method> testMethods = ReflectionUtils.findMethods(testClass, hasTestAnnotation);
+			return !testMethods.isEmpty();
+		}
+	}
+}

junit4-engine/src/main/java/org/junit/gen5/engine/junit4/IsJUnit4TestClassWithTests.java → junit4-engine/src/main/java/org/junit/gen5/engine/junit4/discovery/IsJUnit4TestClassWithTests.java

@@ -8,7 +8,7 @@
  * http://www.eclipse.org/legal/epl-v10.html
  */
 
-package org.junit.gen5.engine.junit4;
+package org.junit.gen5.engine.junit4.discovery;
 
 import static org.junit.gen5.commons.util.ReflectionUtils.MethodSortOrder.HierarchyDown;
 
@@ -20,17 +20,18 @@
 /**
  * @since 5.0
  */
-public class IsJUnit4TestClassWithTests implements Predicate<Class<?>> {
+class IsJUnit4TestClassWithTests implements Predicate<Class<?>> {
 
-	private static final IsJUnit4TestMethod isTestMethod = new IsJUnit4TestMethod();
+	private static final IsPotentialJUnit4TestMethod isTestMethod = new IsPotentialJUnit4TestMethod();
 
 	private static final IsPotentialJUnit4TestClass isPotentialTestClass = new IsPotentialJUnit4TestClass();
 
 	@Override
 	public boolean test(Class<?> testClassCandidate) {
 		if (!isPotentialTestClass.test(testClassCandidate))
 			return false;
-		// Do not use AnnotationUtils.hasAnnotation since JUnit4 does not support meta annotations.
+		// Do not use AnnotationUtils.hasAnnotation since JUnit4 does not support meta
+		// annotations.
 		return testClassCandidate.isAnnotationPresent(RunWith.class) || hasTestMethods(testClassCandidate);
 	}
 

junit4-engine/src/main/java/org/junit/gen5/engine/junit4/IsPotentialJUnit4TestClass.java → junit4-engine/src/main/java/org/junit/gen5/engine/junit4/discovery/IsPotentialJUnit4TestClass.java

@@ -8,17 +8,16 @@
  * http://www.eclipse.org/legal/epl-v10.html
  */
 
-package org.junit.gen5.engine.junit4;
+package org.junit.gen5.engine.junit4.discovery;
 
-import static org.junit.gen5.commons.util.ReflectionUtils.isAbstract;
-import static org.junit.gen5.commons.util.ReflectionUtils.isPublic;
+import static org.junit.gen5.commons.util.ReflectionUtils.*;
 
 import java.util.function.Predicate;
 
 /**
  * @since 5.0
  */
-public class IsPotentialJUnit4TestClass implements Predicate<Class<?>> {
+class IsPotentialJUnit4TestClass implements Predicate<Class<?>> {
 
 	@Override
 	public boolean test(Class<?> candidate) {

junit4-engine/src/main/java/org/junit/gen5/engine/junit4/discovery/IsPotentialJUnit4TestMethod.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2015-2016 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v1.0 which
+ * accompanies this distribution and is available at
+ *
+ * http://www.eclipse.org/legal/epl-v10.html
+ */
+
+package org.junit.gen5.engine.junit4.discovery;
+
+import java.lang.reflect.Method;
+import java.util.function.Predicate;
+
+import org.junit.Test;
+
+/**
+ * @since 5.0
+ */
+class IsPotentialJUnit4TestMethod implements Predicate<Method> {
+
+	@Override
+	public boolean test(Method method) {
+		// Don't use AnnotationUtils.hasAnnotation since JUnit 4 does not support
+		// meta-annotations
+		return method.isAnnotationPresent(Test.class);
+	}
+
+}

junit4-engine/src/main/java/org/junit/gen5/engine/junit4/discovery/JUnit4TestPlanSpecificationResolver.java

@@ -15,39 +15,44 @@
 import org.junit.gen5.engine.TestPlanSpecificationElementVisitor;
 import org.junit.gen5.engine.junit4.descriptor.JUnit4TestDescriptor;
 import org.junit.gen5.engine.junit4.descriptor.RunnerTestDescriptor;
-import org.junit.internal.builders.AllDefaultPossibilitiesBuilder;
 import org.junit.runner.Description;
 import org.junit.runner.Runner;
+import org.junit.runners.model.RunnerBuilder;
 
 public class JUnit4TestPlanSpecificationResolver {
 
-	private EngineDescriptor engineDescriptor;
+	private final EngineDescriptor engineDescriptor;
 
 	public JUnit4TestPlanSpecificationResolver(EngineDescriptor engineDescriptor) {
 		this.engineDescriptor = engineDescriptor;
 	}
 
 	public void resolve(TestPlanSpecification specification) {
+		RunnerBuilder runnerBuilder = new DefensiveAllDefaultPossibilitiesBuilder();
 		specification.accept(new TestPlanSpecificationElementVisitor() {
 
 			@Override
 			public void visitClass(Class<?> testClass) {
-				Runner runner = new AllDefaultPossibilitiesBuilder(true).safeRunnerForClass(testClass);
-
-				RunnerTestDescriptor runnerDescriptor = new RunnerTestDescriptor(engineDescriptor, testClass, runner);
-				addChildrenRecursively(runnerDescriptor);
-
-				engineDescriptor.addChild(runnerDescriptor);
-			}
-
-			private void addChildrenRecursively(JUnit4TestDescriptor parent) {
-				for (Description description : parent.getDescription().getChildren()) {
-					JUnit4TestDescriptor child = new JUnit4TestDescriptor(parent, description);
-					parent.addChild(child);
-					addChildrenRecursively(child);
+				Runner runner = runnerBuilder.safeRunnerForClass(testClass);
+				if (runner != null) {
+					engineDescriptor.addChild(createCompleteRunnerTestDescriptor(testClass, runner));
 				}
 			}
 		});
 	}
 
+	private RunnerTestDescriptor createCompleteRunnerTestDescriptor(Class<?> testClass, Runner runner) {
+		RunnerTestDescriptor runnerTestDescriptor = new RunnerTestDescriptor(engineDescriptor, testClass, runner);
+		addChildrenRecursively(runnerTestDescriptor);
+		return runnerTestDescriptor;
+	}
+
+	private void addChildrenRecursively(JUnit4TestDescriptor parent) {
+		for (Description description : parent.getDescription().getChildren()) {
+			JUnit4TestDescriptor child = new JUnit4TestDescriptor(parent, description);
+			parent.addChild(child);
+			addChildrenRecursively(child);
+		}
+	}
+
 }