Bug 326177 EPartService's getActivePart() does not appear to work properly for an application with multiple windows
Based on the code in PartServiceCreationFunction, the EPartService implementation being returned when an application's context is queried seems to be a window-level EPartService implementation.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
application.setSelectedElement(window);
		
		MPartStack stack = BasicFactoryImpl.eINSTANCE.createPartStack();
		stack.setElementId("category");
		window.getChildren().add(stack);
		window.setSelectedElement(stack);
		MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		stack.getChildren().add(partA);
		stack.setSelectedElement(partA);
		
		initialize(applicationContext, application);
		
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		partService.activate(partA);
		MPart partB = partService.showPart("partId", partState);
		
		assertNotNull("The part should have been rendered", partB.getContext());
	}
	public void testShowPart_Bug307747_CREATE() {
		testShowPart_Bug307747(PartState.CREATE);
	}
	public void testShowPart_Bug307747_VISIBLE() {
		testShowPart_Bug307747(PartState.VISIBLE);
	}
	public void testShowPart_Bug307747_ACTIVATE() {
		testShowPart_Bug307747(PartState.ACTIVATE);
	}
	private void testHidePart_Bug325148(boolean force) {