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
MWindow window = application.getChildren().get(0);
		MPartStack partStack = (MPartStack) window.getChildren().get(0);
		MPart partFront = partStack.getChildren().get(0);
		MPart partBack = partStack.getChildren().get(1);
		partBack.setToBeRendered(false);
		partStack.setSelectedElement(partFront);
		window.setSelectedElement(partStack);
		application.setSelectedElement(window);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		assertFalse(partBack.isToBeRendered());
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		partService.bringToTop(partBack);
		assertTrue("Bringing a part to the top should cause it to be rendered",
				partBack.isToBeRendered());
	}
	public void testGetParts_Empty() {
		MApplication application = createApplication(1, new String[1][0]);
		MWindow window = application.getChildren().get(0);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		Collection<MPart> parts = partService.getParts();
		assertNotNull(parts);
		assertEquals(0, parts.size());
	}
	public void testGetParts_OneWindow() {
		MApplication application = createApplication("partId", "partId2");
		MWindow window = application.getChildren().get(0);