Make @testinstance an @inherited annotation

Issue: #419

Author: sbrannen

Diff for: junit-jupiter-api/src/main/java/org/junit/jupiter/api/TestInstance.java

@@ -12,6 +12,7 @@
 
 import java.lang.annotation.Documented;
 import java.lang.annotation.ElementType;
+import java.lang.annotation.Inherited;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
@@ -22,13 +23,15 @@
  * test class.
  *
  * <p>If {@code @TestInstance} is not declared on a test class, the lifecycle
- * mode will default to {@link Lifecycle#PER_METHOD PER_METHOD}.
+ * mode will default to {@link Lifecycle#PER_METHOD PER_METHOD}. Note, however,
+ * that the lifecycle mode is <em>inherited</em> within test class hierarchies.
  *
  * @author Sam Brannen
  * @since 5.0
  */
 @Target(ElementType.TYPE)
 @Retention(RetentionPolicy.RUNTIME)
+@Inherited
 @Documented
 public @interface TestInstance {
 

Diff for: junit-jupiter-engine/src/test/java/org/junit/jupiter/engine/TestInstanceLifecycleTests.java

@@ -57,17 +57,12 @@
 import org.junit.jupiter.api.extension.TestTemplateInvocationContextProvider;
 import org.junit.platform.commons.util.ReflectionUtils;
 import org.junit.platform.engine.test.event.ExecutionEventRecorder;
-import org.junit.platform.runner.JUnitPlatform;
-import org.junit.runner.RunWith;
 
 /**
  * Integration tests for {@link TestInstance @TestInstance} lifecycle support.
  *
  * @since 5.0
  */
-@RunWith(JUnitPlatform.class)
-public
-
 class TestInstanceLifecycleTests extends AbstractJupiterTestEngineTests {
 
 	private static final Map<String, Object> instanceMap = new LinkedHashMap<>();
@@ -155,7 +150,15 @@ void instancePerMethod() {
 
 	@Test
 	void instancePerClass() {
-		Class<?> testClass = InstancePerClassTestCase.class;
+		instancePerClass(InstancePerClassTestCase.class);
+	}
+
+	@Test
+	void instancePerClassWithInheritedLifecycleMode() {
+		instancePerClass(SubInstancePerClassTestCase.class);
+	}
+
+	private void instancePerClass(Class<?> testClass) {
 		int containers = 3;
 		int tests = 3;
 		int instances = 1;
@@ -475,8 +478,6 @@ private void performAssertions(Class<?> testClass, int containers, int tests, in
 
 		ExecutionEventRecorder eventRecorder = executeTestsForClass(testClass);
 
-		// eventRecorder.eventStream().forEach(System.out::println);
-
 		// @formatter:off
 		assertAll(
 			() -> assertEquals(containers, eventRecorder.getContainerStartedCount(), "# containers started"),
@@ -584,7 +585,7 @@ static void afterAllStatic(TestInfo testInfo) {
 	}
 
 	@TestInstance(Lifecycle.PER_CLASS)
-	private static class InstancePerClassTestCase extends InstancePerMethodTestCase {
+	static class InstancePerClassTestCase extends InstancePerMethodTestCase {
 
 		@BeforeAll
 		void beforeAll(TestInfo testInfo) {
@@ -600,6 +601,9 @@ void afterAll(TestInfo testInfo) {
 
 	}
 
+	private static class SubInstancePerClassTestCase extends InstancePerClassTestCase {
+	}
+
 	@ExtendWith(InstanceTrackingExtension.class)
 	// The following is commented out b/c it's the default.
 	// @TestInstance(Lifecycle.PER_METHOD)