Bug 303218 Active part no longer seems to be queryable from the application's context
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
MPartStack stack = MApplicationFactory.eINSTANCE.createPartStack();
		stack.setId("stackId");
		window.getChildren().add(stack);
		MPartDescriptor partDescriptor = MApplicationFactory.eINSTANCE
				.createPartDescriptor();
		partDescriptor.setId("part");
		partDescriptor.setCategory("stackId");
		application.getDescriptors().add(partDescriptor);
		application.setSelectedElement(window);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		MPart part = partService.showPart("part",
				EPartService.PartState.VISIBLE);
		assertEquals(1, stack.getChildren().size());
		assertEquals(part, stack.getChildren().get(0));
		assertEquals(part, partService.getActivePart());
	}
	public void testShowPart_Id_VISIBLE5() {
		MApplication application = MApplicationFactory.eINSTANCE
				.createApplication();
		MWindow window = MApplicationFactory.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPartDescriptor partDescriptor = MApplicationFactory.eINSTANCE
				.createPartDescriptor();
		partDescriptor.setId("partB");
		partDescriptor.setCategory("aCategory");
		application.getDescriptors().add(partDescriptor);
		MPartStack partStack = MApplicationFactory.eINSTANCE.createPartStack();