Bug 41798 New JUnit Plug-in test requires test suites to extend Test
The new JUnit plug-in test seems to require test suites to extend TestSuite. Otherwise an error is reported in the launch config dialog. It is however still possible to launch a test suite by opening it in the editor and choosing Run->Run As->New JUnit Plug-in Test To reproduce, try to run (and configure) the JDT UI AllAllTests testsuite.
org.eclipse.jdt.junit.core/src/org/eclipse/jdt/internal/junit/util/TestSearchEngine.java
} 
		else if (element instanceof IJavaElement) {
			List found= searchSuiteMethods(pm, (IJavaElement)element);
			result.addAll(found);
		}
	}
	private static Object computeScope(Object element) throws JavaModelException {
		if (element instanceof IFileEditorInput)
			element= ((IFileEditorInput)element).getFile();
		if (element instanceof IResource)
			element= JavaCore.create((IResource)element);
		if (element instanceof IClassFile) {
			IClassFile cf= (IClassFile)element;
			element= cf.getType();
		}
		return element;
	}
	
	private static List searchSuiteMethods(IProgressMonitor pm, IJavaElement element) throws JavaModelException {	
		IJavaSearchScope scope= SearchEngine.createJavaSearchScope(new IJavaElement[] { element });
		TestSearchEngine searchEngine= new TestSearchEngine(); 
		return searchEngine.searchMethod(pm, scope);
	}
		
	private static boolean hasSuiteMethod(IType type) throws JavaModelException {
		IMethod method= type.getMethod("suite", new String[0]); 
		if (method == null || !method.exists()) 
			return false;
		
		if (!Flags.isStatic(method.getFlags()) ||