Remove null support from getWrapperType input, add test coverage

Author: scordio

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

@@ -238,7 +238,7 @@ public enum HierarchyTraversalMode {
 
 		classNameToTypeMap = Collections.unmodifiableMap(classNamesToTypes);
 
-		Map<Class<?>, Class<?>> primitivesToWrappers = new IdentityHashMap<>(9);
+		Map<Class<?>, Class<?>> primitivesToWrappers = new IdentityHashMap<>(8);
 
 		primitivesToWrappers.put(boolean.class, Boolean.class);
 		primitivesToWrappers.put(byte.class, Byte.class);
@@ -564,7 +564,7 @@ static boolean isWideningConversion(Class<?> sourceType, Class<?> targetType) {
 	 *
 	 * @param type the primitive type for which to retrieve the wrapper type
 	 * @return the corresponding wrapper type or {@code null} if the
-	 * supplied type is {@code null} or not a primitive type
+	 * supplied type is not a primitive type
 	 */
 	public static @Nullable Class<?> getWrapperType(Class<?> type) {
 		return primitiveToWrapperMap.get(type);

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

@@ -20,6 +20,7 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTimeoutPreemptively;
 import static org.junit.jupiter.api.Assertions.assertTrue;
@@ -213,6 +214,19 @@ void wideningConversion() {
 			assertFalse(isWideningConversion(String.class, int.class)); // neither a primitive nor a wrapper
 		}
 
+		@Test
+		void getWrapperType() {
+			assertEquals(Boolean.class, ReflectionUtils.getWrapperType(boolean.class));
+			assertEquals(Byte.class, ReflectionUtils.getWrapperType(byte.class));
+			assertEquals(Character.class, ReflectionUtils.getWrapperType(char.class));
+			assertEquals(Short.class, ReflectionUtils.getWrapperType(short.class));
+			assertEquals(Integer.class, ReflectionUtils.getWrapperType(int.class));
+			assertEquals(Long.class, ReflectionUtils.getWrapperType(long.class));
+			assertEquals(Float.class, ReflectionUtils.getWrapperType(float.class));
+			assertEquals(Double.class, ReflectionUtils.getWrapperType(double.class));
+			assertNull(ReflectionUtils.getWrapperType(Object.class));
+		}
+
 		@Test
 		void getAllClasspathRootDirectories(@TempDir Path tempDirectory) throws Exception {
 			var root1 = tempDirectory.resolve("root1").toAbsolutePath();