Fall back to display name if method name is blank

Prior to this commit, `VintageTestDescriptor` used the `Description`'s
method name when it wasn't null. However, there are edge cases where it
can be empty which lead to blank display names which are not allowed by
the Platform. Thus, it is now only used if not blank.

Fixes #2248.

junit-vintage-engine/src/main/java/org/junit/vintage/engine/descriptor/VintageTestDescriptor.java

@@ -55,7 +55,8 @@ public VintageTestDescriptor(UniqueId uniqueId, Description description, TestSou
 	}
 
 	private static String generateDisplayName(Description description) {
-		return description.getMethodName() != null ? description.getMethodName() : description.getDisplayName();
+		String methodName = description.getMethodName();
+		return isNotBlank(methodName) ? methodName : description.getDisplayName();
 	}
 
 	public Description getDescription() {

junit-vintage-engine/src/test/java/org/junit/vintage/engine/VintageTestEngineDiscoveryTests.java

@@ -58,12 +58,12 @@
 import org.junit.vintage.engine.samples.junit4.Categories.SkippedWithReason;
 import org.junit.vintage.engine.samples.junit4.EmptyIgnoredTestCase;
 import org.junit.vintage.engine.samples.junit4.IgnoredJUnit4TestCase;
+import org.junit.vintage.engine.samples.junit4.JUnit4SuiteWithJUnit4TestCaseWithRunnerWithCustomUniqueIdsAndDisplayNames;
 import org.junit.vintage.engine.samples.junit4.JUnit4SuiteWithPlainJUnit4TestCaseWithSingleTestWhichIsIgnored;
 import org.junit.vintage.engine.samples.junit4.JUnit4SuiteWithTwoTestCases;
 import org.junit.vintage.engine.samples.junit4.JUnit4TestCaseWithDistinguishableOverloadedMethod;
 import org.junit.vintage.engine.samples.junit4.JUnit4TestCaseWithIndistinguishableOverloadedMethod;
 import org.junit.vintage.engine.samples.junit4.JUnit4TestCaseWithNotFilterableRunner;
-import org.junit.vintage.engine.samples.junit4.JUnit4TestCaseWithRunnerWithCustomUniqueIds;
 import org.junit.vintage.engine.samples.junit4.ParameterizedTestCase;
 import org.junit.vintage.engine.samples.junit4.PlainJUnit4TestCaseWithFiveTestMethods;
 import org.junit.vintage.engine.samples.junit4.PlainJUnit4TestCaseWithSingleInheritedTestWhichFails;
@@ -662,19 +662,23 @@ void resolvesClassForMethodSelectorForClassWithNonFilterableRunner() {
 	}
 
 	@Test
-	void usesCustomUniqueIdsWhenPresent() {
-		Class<?> testClass = JUnit4TestCaseWithRunnerWithCustomUniqueIds.class;
-		LauncherDiscoveryRequest request = request().selectors(selectClass(testClass)).build();
+	void usesCustomUniqueIdsAndDisplayNamesWhenPresent() {
+		Class<?> suiteClass = JUnit4SuiteWithJUnit4TestCaseWithRunnerWithCustomUniqueIdsAndDisplayNames.class;
+		LauncherDiscoveryRequest request = request().selectors(selectClass(suiteClass)).build();
 
 		TestDescriptor engineDescriptor = discoverTests(request);
 
 		TestDescriptor runnerDescriptor = getOnlyElement(engineDescriptor.getChildren());
-		assertRunnerTestDescriptor(runnerDescriptor, testClass);
+		assertRunnerTestDescriptor(runnerDescriptor, suiteClass);
 
-		TestDescriptor childDescriptor = getOnlyElement(runnerDescriptor.getChildren());
+		TestDescriptor testClassDescriptor = getOnlyElement(runnerDescriptor.getChildren());
+		assertEquals("(TestClass)", testClassDescriptor.getDisplayName());
+
+		TestDescriptor childDescriptor = getOnlyElement(testClassDescriptor.getChildren());
 
-		UniqueId prefix = VintageUniqueIdBuilder.uniqueIdForClass(testClass);
+		UniqueId prefix = VintageUniqueIdBuilder.uniqueIdForClass(suiteClass);
 		assertThat(childDescriptor.getUniqueId().toString()).startsWith(prefix.toString());
+		assertEquals("(TestMethod)", childDescriptor.getDisplayName());
 
 		String customUniqueIdValue = childDescriptor.getUniqueId().getSegments().get(2).getType();
 		assertNotNull(Base64.getDecoder().decode(customUniqueIdValue.getBytes(StandardCharsets.UTF_8)),

junit-vintage-engine/src/test/java/org/junit/vintage/engine/VintageTestEngineExecutionTests.java

@@ -75,7 +75,7 @@
 import org.junit.vintage.engine.samples.junit4.JUnit4TestCaseWithExceptionThrowingRunner;
 import org.junit.vintage.engine.samples.junit4.JUnit4TestCaseWithFailingDescriptionThatIsNotReportedAsFinished;
 import org.junit.vintage.engine.samples.junit4.JUnit4TestCaseWithIndistinguishableOverloadedMethod;
-import org.junit.vintage.engine.samples.junit4.JUnit4TestCaseWithRunnerWithCustomUniqueIds;
+import org.junit.vintage.engine.samples.junit4.JUnit4TestCaseWithRunnerWithCustomUniqueIdsAndDisplayNames;
 import org.junit.vintage.engine.samples.junit4.JUnit4TestCaseWithRunnerWithDuplicateChangingChildDescriptions;
 import org.junit.vintage.engine.samples.junit4.MalformedJUnit4TestCase;
 import org.junit.vintage.engine.samples.junit4.ParameterizedTestCase;
@@ -610,7 +610,7 @@ void ignoreEventsForUnknownDescriptionsByMisbehavingChildlessRunner() {
 
 	@Test
 	void executesJUnit4TestCaseWithRunnerWithCustomUniqueIds() {
-		Class<?> testClass = JUnit4TestCaseWithRunnerWithCustomUniqueIds.class;
+		Class<?> testClass = JUnit4TestCaseWithRunnerWithCustomUniqueIdsAndDisplayNames.class;
 
 		execute(testClass).allEvents().assertEventsMatchExactly( //
 			event(engine(), started()), //

junit-vintage-engine/src/test/java/org/junit/vintage/engine/samples/junit4/JUnit4SuiteWithJUnit4TestCaseWithRunnerWithCustomUniqueIdsAndDisplayNames.java

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2015-2020 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 v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junit.vintage.engine.samples.junit4;
+
+import org.junit.runner.RunWith;
+import org.junit.runners.Suite;
+import org.junit.runners.Suite.SuiteClasses;
+
+/**
+ * @since 5.6.2
+ */
+@RunWith(Suite.class)
+@SuiteClasses(JUnit4TestCaseWithRunnerWithCustomUniqueIdsAndDisplayNames.class)
+public class JUnit4SuiteWithJUnit4TestCaseWithRunnerWithCustomUniqueIdsAndDisplayNames {
+}

junit-vintage-engine/src/test/java/org/junit/vintage/engine/samples/junit4/JUnit4TestCaseWithRunnerWithCustomUniqueIds.java → junit-vintage-engine/src/test/java/org/junit/vintage/engine/samples/junit4/JUnit4TestCaseWithRunnerWithCustomUniqueIdsAndDisplayNames.java

@@ -12,15 +12,18 @@
 
 import org.junit.Assert;
 import org.junit.Test;
+import org.junit.jupiter.api.DisplayName;
 import org.junit.runner.RunWith;
 
 /**
  * @since 4.12
  */
-@RunWith(RunnerWithCustomUniqueIds.class)
-public class JUnit4TestCaseWithRunnerWithCustomUniqueIds {
+@DisplayName("(TestClass)")
+@RunWith(RunnerWithCustomUniqueIdsAndDisplayNames.class)
+public class JUnit4TestCaseWithRunnerWithCustomUniqueIdsAndDisplayNames {
 
 	@Test
+	@DisplayName("(TestMethod)")
 	public void test() {
 		Assert.fail();
 	}

junit-vintage-engine/src/test/java/org/junit/vintage/engine/samples/junit4/RunnerWithCustomUniqueIds.java → junit-vintage-engine/src/test/java/org/junit/vintage/engine/samples/junit4/RunnerWithCustomUniqueIdsAndDisplayNames.java

@@ -15,6 +15,7 @@
 import java.io.Serializable;
 import java.util.Objects;
 
+import org.junit.jupiter.api.DisplayName;
 import org.junit.runner.Description;
 import org.junit.runners.BlockJUnit4ClassRunner;
 import org.junit.runners.model.FrameworkMethod;
@@ -23,18 +24,29 @@
 /**
  * @since 4.12
  */
-public class RunnerWithCustomUniqueIds extends BlockJUnit4ClassRunner {
+public class RunnerWithCustomUniqueIdsAndDisplayNames extends BlockJUnit4ClassRunner {
 
-	public RunnerWithCustomUniqueIds(Class<?> klass) throws InitializationError {
+	public RunnerWithCustomUniqueIdsAndDisplayNames(Class<?> klass) throws InitializationError {
 		super(klass);
 	}
 
+	@Override
+	protected String getName() {
+		DisplayName displayName = getTestClass().getAnnotation(DisplayName.class);
+		return displayName == null ? super.getName() : displayName.value();
+	}
+
 	@Override
 	protected Description describeChild(FrameworkMethod method) {
-		String testName = testName(method);
+		String testName = getTestName(method);
 		return createTestDescription(getTestClass().getJavaClass().getName(), testName, new CustomUniqueId(testName));
 	}
 
+	private String getTestName(FrameworkMethod method) {
+		DisplayName displayName = method.getAnnotation(DisplayName.class);
+		return displayName == null ? testName(method) : displayName.value();
+	}
+
 	private static class CustomUniqueId implements Serializable {
 
 		private static final long serialVersionUID = 1L;