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
collectTypes(elements[i], new SubProgressMonitor(pm, 1), result);
				} catch (JavaModelException e) {
					JUnitPlugin.log(e.getStatus());
				}
				if (pm.isCanceled()) {
					throw new InterruptedException();
				}
			}
		} finally {
			pm.done();
		}
	}
	private static void collectTypes(Object element, IProgressMonitor pm, Set result) throws JavaModelException {
		element= computeScope(element);
		while((element instanceof IJavaElement) && !(element instanceof ICompilationUnit) && (element instanceof ISourceReference)) {
			if(element instanceof IType) {
				if (hasSuiteMethod((IType)element) || isTestType((IType)element)) {
					result.add(element);
					return;
				}
			}
			element= ((IJavaElement)element).getParent();
		}
		if (element instanceof ICompilationUnit) {
			ICompilationUnit cu= (ICompilationUnit)element;
			IType[] types= cu.getAllTypes();
			for (int i= 0; i < types.length; i++) {
				if (hasSuiteMethod(types[i])  || isTestType(types[i]))
					result.add(types[i]);
			}