Bug 307747 EPartService doesn't render new parts
1. Have a part in a stack, it is the selected part. 2. Show another part in that stack using PartState.CREATE or PartState.VISIBLE. 3. The part should've been rendered. It is not.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
MWindow window = MApplicationFactory.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPartDescriptor partDescriptor = MApplicationFactory.eINSTANCE
				.createPartDescriptor();
		partDescriptor.setId("partId");
		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.createPart("partId");
		partService.showPart(part, partState);
	}
	public void testShowPart_Part_ACTIVATE() {
		testShowPart_Part(PartState.ACTIVATE);
	}
	public void testShowPart_Part_VISIBLE() {
		testShowPart_Part(PartState.VISIBLE);
	}
	public void testShowPart_Part_CREATE() {
		testShowPart_Part(PartState.CREATE);
	}
	private void testShowPart_Part_MultipleExists(boolean multipleAllowed,
			PartState partState) {
		MApplication application = createApplication("partId");
		MWindow window = application.getChildren().get(0);
		MPartStack stack = (MPartStack) window.getChildren().get(0);
		MPart part = stack.getChildren().get(0);
		MPartDescriptor partDescriptor = MApplicationFactory.eINSTANCE