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/src/org/eclipse/jdt/internal/junit/util/TestSearchEngine.java
if (!(enclosingElement instanceof IMethod)) 
				return;
			
			IMethod method= (IMethod)enclosingElement;		
			
			IType declaringType= method.getDeclaringType();
			if (fMatches.contains(declaringType) || fFailed.contains(declaringType))
				return;
			if (!hasSuiteMethod(declaringType) && !isTestType(declaringType)) {
				fFailed.add(declaringType);
				return;
			}
			fMatches.add(declaringType);
		}
		
		public IProgressMonitor getProgressMonitor() {
			return fProgressMonitor;
		}
				
		public void aboutToStart() {
		}
		
		public void done() {
			fList.addAll(fMatches);
		}
	}
	
	private List searchMethod(IProgressMonitor pm, final IJavaSearchScope scope) throws JavaModelException {
		final List typesFound= new ArrayList(200);	
		searchMethod(typesFound, scope, pm);