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
MPart partFrontB = MApplicationFactory.eINSTANCE.createPart();
		MPart partBackB = MApplicationFactory.eINSTANCE.createPart();
		partStackB.getChildren().add(partFrontB);
		partStackB.getChildren().add(partBackB);
		window.getChildren().add(partStackB);
		partStackA.setSelectedElement(partFrontA);
		partStackB.setSelectedElement(partFrontB);
		window.setSelectedElement(partStackA);
		application.setSelectedElement(window);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		partService.activate(partFrontA);
		assertEquals(partFrontA, partService.getActivePart());
		partService.bringToTop(partBackB);
		assertEquals(partFrontA, partService.getActivePart());
		assertTrue(partService.isPartVisible(partFrontA));
		assertFalse(partService.isPartVisible(partBackA));
		assertFalse(partService.isPartVisible(partFrontB));
		assertTrue(partService.isPartVisible(partBackB));
		partService.bringToTop(partBackA);
		assertEquals(partBackA, partService.getActivePart());
		assertFalse(partService.isPartVisible(partFrontA));
		assertTrue(partService.isPartVisible(partBackA));
		assertFalse(partService.isPartVisible(partFrontB));
		assertTrue(partService.isPartVisible(partBackB));
	}
	public void testBringToTop_Unrendered() {
		MApplication application = createApplication("partFront", "partBack");