Generate proper default display name for test methods

This commit revises the default display generation for test methods so
that the following format is used instead of simply the method name.

 - <name>([comma separated list of simple names for parameter types])

Issue: #153

documentation/src/test/java/example/TestInfoDemo.java

@@ -25,7 +25,7 @@ class TestInfoDemo {
 	@BeforeEach
 	void init(TestInfo testInfo) {
 		String displayName = testInfo.getDisplayName();
-		assertTrue(displayName.equals("TEST 1") || displayName.equals("test2"));
+		assertTrue(displayName.equals("TEST 1") || displayName.equals("test2()"));
 	}
 
 	@Test

junit-commons/src/main/java/org/junit/gen5/commons/util/StringUtils.java

@@ -14,6 +14,8 @@
 import static java.util.stream.Collectors.joining;
 import static org.junit.gen5.commons.meta.API.Usage.Internal;
 
+import java.util.function.Function;
+
 import org.junit.gen5.commons.meta.API;
 
 /**
@@ -62,19 +64,36 @@ public static boolean isNotBlank(String str) {
 	}
 
 	/**
-	 * Generate a comma-separated list of class names for the supplied
-	 * classes.
+	 * Generate a comma-separated list of fully qualified class names for the
+	 * supplied classes.
 	 *
 	 * @param classes the classes whose names should be included in the
 	 * generated string
-	 * @return a comma-separated list of class names, or an empty string if
-	 * the supplied class array is {@code null} or empty
+	 * @return a comma-separated list of fully qualified class names, or an empty
+	 * string if the supplied class array is {@code null} or empty
+	 * @see #nullSafeToString(Function, Class...)
 	 */
 	public static String nullSafeToString(Class<?>... classes) {
+		return nullSafeToString(Class::getName, classes);
+	}
+
+	/**
+	 * Generate a comma-separated list of mapped values for the supplied classes.
+	 *
+	 * <p>The values are generated by the supplied {@code mapper}
+	 * (e.g., {@code Class::getName}, {@code Class::getSimpleName}, etc.).
+	 *
+	 * @param mapper the mapper to use
+	 * @param classes the classes to map
+	 * @return a comma-separated list of mapped values, or an empty string if
+	 * the supplied class array is {@code null} or empty
+	 * @see #nullSafeToString(Class...)
+	 */
+	public static String nullSafeToString(Function<? super Class<?>, ? extends String> mapper, Class<?>... classes) {
 		if (classes == null || classes.length == 0) {
 			return "";
 		}
-		return stream(classes).map(Class::getName).collect(joining(", "));
+		return stream(classes).map(mapper).collect(joining(", "));
 	}
 
 }

junit-tests/src/test/java/org/junit/gen5/engine/junit5/descriptor/JUnit5TestDescriptorTests.java

@@ -45,7 +45,7 @@ public void constructFromMethod() throws Exception {
 
 		assertEquals(UniqueId.root("method", "a method id"), descriptor.getUniqueId());
 		assertEquals(testMethod, descriptor.getTestMethod());
-		assertEquals("test", descriptor.getDisplayName(), "display name:");
+		assertEquals("test()", descriptor.getDisplayName(), "display name:");
 	}
 
 	@Test
@@ -98,7 +98,7 @@ public void constructFromMethodWithParameters() throws Exception {
 			ASampleTestCase.class, testMethod);
 
 		assertEquals(testMethod, descriptor.getTestMethod());
-		assertEquals("test", descriptor.getDisplayName(), "display name:");
+		assertEquals("test(String, BigDecimal)", descriptor.getDisplayName(), "display name:");
 	}
 
 	@Tag("classTag1")

junit-tests/src/test/java/org/junit/gen5/engine/junit5/extension/TestInfoParameterResolverTests.java

@@ -10,12 +10,12 @@
 
 package org.junit.gen5.engine.junit5.extension;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.gen5.api.Assertions.assertEquals;
 import static org.junit.gen5.api.Assertions.assertTrue;
 
 import java.util.Arrays;
-import java.util.HashSet;
-import java.util.Set;
+import java.util.List;
 
 import org.junit.gen5.api.AfterAll;
 import org.junit.gen5.api.AfterEach;
@@ -27,17 +27,19 @@
 import org.junit.gen5.api.TestInfo;
 
 /**
- * Integration tests for {@link TestInfoParameterResolver}
+ * Integration tests for {@link TestInfoParameterResolver}.
+ *
+ * @since 5.0
  */
 @Tag("class-tag")
 class TestInfoParameterResolverTests {
 
-	private Set<String> allDisplayNames = new HashSet<>(
-		Arrays.asList(new String[] { "getName", "defaultDisplayName", "myName", "getTags" }));
+	private static List<String> allDisplayNames = Arrays.asList("defaultDisplayName(TestInfo)", "myName",
+		"getTags(TestInfo)");
 
 	@Test
 	void defaultDisplayName(TestInfo testInfo) {
-		assertEquals("defaultDisplayName", testInfo.getDisplayName());
+		assertEquals("defaultDisplayName(TestInfo)", testInfo.getDisplayName());
 	}
 
 	@Test
@@ -55,13 +57,9 @@ void getTags(TestInfo testInfo) {
 	}
 
 	@BeforeEach
-	void before(TestInfo testInfo) {
-		assertTrue(allDisplayNames.contains(testInfo.getDisplayName()));
-	}
-
 	@AfterEach
-	void after(TestInfo testInfo) {
-		assertTrue(allDisplayNames.contains(testInfo.getDisplayName()));
+	void beforeAndAfter(TestInfo testInfo) {
+		assertThat(allDisplayNames).contains(testInfo.getDisplayName());
 	}
 
 	@BeforeAll

junit5-engine/src/main/java/org/junit/gen5/engine/junit5/descriptor/ClassTestDescriptor.java

@@ -74,7 +74,7 @@ public ClassTestDescriptor(UniqueId uniqueId, Class<?> testClass) {
 		super(uniqueId);
 
 		this.testClass = Preconditions.notNull(testClass, "Class must not be null");
-		this.displayName = determineDisplayName(testClass, testClass.getName());
+		this.displayName = determineDisplayName(testClass, () -> testClass.getName());
 
 		this.beforeAllMethods = findBeforeAllMethods(testClass);
 		this.afterAllMethods = findAfterAllMethods(testClass);

junit5-engine/src/main/java/org/junit/gen5/engine/junit5/descriptor/JUnit5TestDescriptor.java

@@ -21,6 +21,7 @@
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
+import java.util.function.Supplier;
 
 import org.junit.gen5.api.DisplayName;
 import org.junit.gen5.api.Executable;
@@ -55,12 +56,12 @@ protected Set<TestTag> getTags(AnnotatedElement element) {
 		// @formatter:on
 	}
 
-	protected String determineDisplayName(AnnotatedElement element, String defaultName) {
+	protected String determineDisplayName(AnnotatedElement element, Supplier<String> defaultNameGenerator) {
 		// @formatter:off
 		return findAnnotation(element, DisplayName.class)
 				.map(DisplayName::value)
 				.filter(StringUtils::isNotBlank)
-				.orElse(defaultName);
+				.orElse(defaultNameGenerator.get());
 		// @formatter:on
 	}
 

junit5-engine/src/main/java/org/junit/gen5/engine/junit5/descriptor/MethodTestDescriptor.java

@@ -29,6 +29,7 @@
 import org.junit.gen5.commons.meta.API;
 import org.junit.gen5.commons.util.ExceptionUtils;
 import org.junit.gen5.commons.util.Preconditions;
+import org.junit.gen5.commons.util.StringUtils;
 import org.junit.gen5.engine.TestDescriptor;
 import org.junit.gen5.engine.TestTag;
 import org.junit.gen5.engine.UniqueId;
@@ -63,11 +64,7 @@ public MethodTestDescriptor(UniqueId uniqueId, Class<?> testClass, Method testMe
 
 		this.testClass = Preconditions.notNull(testClass, "Class must not be null");
 		this.testMethod = Preconditions.notNull(testMethod, "Method must not be null");
-
-		// TODO Generate proper default display name.
-		// String.format("%s#%s(%s)", getTestClass().getName(), this.testMethod.getName(),
-		// StringUtils.nullSafeToString(this.testMethod.getParameterTypes()));
-		this.displayName = determineDisplayName(testMethod, testMethod.getName());
+		this.displayName = determineDisplayName(testMethod, () -> generateDefaultDisplayName(testMethod));
 
 		setSource(new JavaMethodSource(testMethod));
 	}
@@ -220,4 +217,9 @@ private void invokeAfterEachCallbacks(ExtensionRegistry registry, TestExtensionC
 				.forEach(extension -> throwableCollector.execute(() -> extension.afterEach(context)));
 	}
 
+	private static String generateDefaultDisplayName(Method method) {
+		return String.format("%s(%s)", method.getName(),
+			StringUtils.nullSafeToString(Class::getSimpleName, method.getParameterTypes()));
+	}
+
 }