Support void and Void class lookups in ReflectionUtils (#4049)

Both the primitive type `void` and the wrapper type `Void` are now 
supported in the internal `ReflectionUtils` to allow `String` to `Class`
conversion in parameterized tests.

Fixes #4048.

---------

Co-authored-by: Marc Philipp <[email protected]>

Author: bjmi

documentation/src/docs/asciidoc/release-notes/release-notes-5.12.0-M1.adoc

@@ -29,6 +29,8 @@ JUnit repository on GitHub.
 
 * Introduce `ReflectionSupport.makeAccessible(Field)` for third-party use rather than
   calling the internal `ReflectionUtils.makeAccessible(Field)` method directly.
+* Support both the primitive type `void` and the wrapper type `Void` in the internal
+  `ReflectionUtils` to support `String` to `Class` conversion in parameterized tests.
 
 
 [[release-notes-5.12.0-M1-junit-jupiter]]

junit-platform-commons/src/main/java/org/junit/platform/commons/util/ReflectionUtils.java

@@ -186,6 +186,7 @@ public enum HierarchyTraversalMode {
 			long.class,
 			float.class,
 			double.class,
+			void.class,
 
 			boolean[].class,
 			byte[].class,
@@ -213,6 +214,7 @@ public enum HierarchyTraversalMode {
 			Long.class,
 			Float.class,
 			Double.class,
+			Void.class,
 			String.class,
 
 			Boolean[].class,
@@ -246,7 +248,7 @@ public enum HierarchyTraversalMode {
 
 		classNameToTypeMap = Collections.unmodifiableMap(classNamesToTypes);
 
-		Map<Class<?>, Class<?>> primitivesToWrappers = new IdentityHashMap<>(8);
+		Map<Class<?>, Class<?>> primitivesToWrappers = new IdentityHashMap<>(9);
 
 		primitivesToWrappers.put(boolean.class, Boolean.class);
 		primitivesToWrappers.put(byte.class, Byte.class);
@@ -256,6 +258,7 @@ public enum HierarchyTraversalMode {
 		primitivesToWrappers.put(long.class, Long.class);
 		primitivesToWrappers.put(float.class, Float.class);
 		primitivesToWrappers.put(double.class, Double.class);
+		primitivesToWrappers.put(void.class, Void.class);
 
 		primitiveToWrapperMap = Collections.unmodifiableMap(primitivesToWrappers);
 	}

jupiter-tests/src/test/java/org/junit/jupiter/params/converter/DefaultArgumentConverterTests.java

@@ -132,7 +132,7 @@ void convertsStringsToPrimitiveWrapperTypes() {
 
 	@ParameterizedTest(name = "[{index}] {0}")
 	@ValueSource(classes = { char.class, boolean.class, short.class, byte.class, int.class, long.class, float.class,
-			double.class })
+			double.class, void.class })
 	void throwsExceptionForNullToPrimitiveTypeConversion(Class<?> type) {
 		assertThatExceptionOfType(ArgumentConversionException.class) //
 				.isThrownBy(() -> convert(null, type)) //
@@ -261,8 +261,10 @@ void convertsStringToPath() {
 	@Test
 	void convertsStringToClass() {
 		assertConverts("java.lang.Integer", Class.class, Integer.class);
+		assertConverts("java.lang.Void", Class.class, Void.class);
 		assertConverts("java.lang.Thread$State", Class.class, State.class);
 		assertConverts("byte", Class.class, byte.class);
+		assertConverts("void", Class.class, void.class);
 		assertConverts("char[]", Class.class, char[].class);
 		assertConverts("java.lang.Long[][]", Class.class, Long[][].class);
 		assertConverts("[[[I", Class.class, int[][][].class);

platform-tests/src/test/java/org/junit/platform/commons/util/ReflectionUtilsTests.java

@@ -559,6 +559,7 @@ void isAssignableTo() {
 			// Wrappers to Primitives
 			assertTrue(ReflectionUtils.isAssignableTo(Integer.class, int.class));
 			assertTrue(ReflectionUtils.isAssignableTo(Boolean.class, boolean.class));
+			assertTrue(ReflectionUtils.isAssignableTo(Void.class, void.class));
 
 			// Widening Conversions from Wrappers to Primitives
 			assertTrue(ReflectionUtils.isAssignableTo(Integer.class, long.class));
@@ -759,6 +760,7 @@ void loadClass() {
 		@Test
 		void tryToLoadClass() {
 			assertThat(ReflectionUtils.tryToLoadClass(Integer.class.getName())).isEqualTo(success(Integer.class));
+			assertThat(ReflectionUtils.tryToLoadClass(Void.class.getName())).isEqualTo(success(Void.class));
 		}
 
 		@Test
@@ -770,6 +772,7 @@ void tryToLoadClassTrimsClassName() {
 		@Test
 		void tryToLoadClassForPrimitive() {
 			assertThat(ReflectionUtils.tryToLoadClass(int.class.getName())).isEqualTo(success(int.class));
+			assertThat(ReflectionUtils.tryToLoadClass(void.class.getName())).isEqualTo(success(void.class));
 		}
 
 		@Test