Introduce test for scanning classes in a modular JAR

Addresses #2500

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

@@ -18,6 +18,7 @@
 import static org.junit.jupiter.api.Assumptions.assumeFalse;
 
 import java.io.IOException;
+import java.lang.module.ModuleFinder;
 import java.net.URI;
 import java.net.URL;
 import java.net.URLClassLoader;
@@ -27,6 +28,7 @@
 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.List;
+import java.util.Set;
 import java.util.function.BiFunction;
 import java.util.function.Predicate;
 import java.util.logging.Level;
@@ -176,6 +178,26 @@ void scanForClassesInPackage() {
 		assertTrue(classes.contains(MemberClassToBeFound.class));
 	}
 
+	@Test
+	// #2500
+	void scanForClassesInPackageWithinModuleSharingNames() throws Exception {
+		var jarfile = getClass().getResource("/[email protected]");
+
+		var module = "com.greetings";
+		var before = ModuleFinder.of();
+		var finder = ModuleFinder.of(Path.of(jarfile.toURI()));
+		var boot = ModuleLayer.boot();
+		var configuration = boot.configuration().resolveAndBind(before, finder, Set.of(module));
+		var parent = ClassLoader.getPlatformClassLoader();
+		var layer = ModuleLayer.defineModulesWithOneLoader(configuration, List.of(boot), parent).layer();
+
+		var classpathScanner = new ClasspathScanner(() -> layer.findLoader(module), ReflectionUtils::tryToLoadClass);
+
+		var classes = classpathScanner.scanForClassesInPackage("com.greetings", allClasses);
+		var classNames = classes.stream().map(Class::getName).collect(Collectors.toList());
+		assertThat(classNames).hasSize(1).contains("com.greetings.Main");
+	}
+
 	@Test
 	void findAllClassesInPackageWithinJarFile() throws Exception {
 		var jarfile = getClass().getResource("/jartest.jar");