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
MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPerspectiveStack perspectiveStack = AdvancedFactoryImpl.eINSTANCE
				.createPerspectiveStack();
		window.getChildren().add(perspectiveStack);
		window.setSelectedElement(perspectiveStack);
		MPerspective perspective = AdvancedFactoryImpl.eINSTANCE
				.createPerspective();
		perspectiveStack.getChildren().add(perspective);
		perspectiveStack.setSelectedElement(perspective);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = window.getContext().get(EPartService.class);
		MPlaceholder placeholder = partService.createSharedPart("partId", true);
		MPart sharedPart = (MPart) placeholder.getRef();
		sharedPart.setCurSharedRef(placeholder);
		placeholder.setToBeRendered(false);
		sharedPart.setToBeRendered(false);
		perspective.getChildren().add(placeholder);
		partService.showPart(sharedPart, partState);
		assertNotNull(perspective.getSelectedElement());
		assertEquals(placeholder, perspective.getSelectedElement());
	}
	public void testShowPart_Bug322368_Placeholder_ACTIVATE() {
		testShowPart_Bug322368_Placeholder(PartState.ACTIVATE);
	}
	public void testShowPart_Bug322368_Placeholder_VISIBLE() {
		testShowPart_Bug322368_Placeholder(PartState.VISIBLE);
	}