Bug 328946 Part activation history may return incorrect candidate if no placeholders could be found in a perspective
1. Window > Open Perspective > Other... > CVS Repository Exploring 2. Hide the 'CVS Repositories' view. 3. The 'History' view should become active, it is not.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
perspective.setSelectedElement(partStack);
		MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		partStack.getChildren().add(partA);
		partStack.setSelectedElement(partA);
		MPlaceholder placeholderB = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		partB.setCurSharedRef(placeholderB);
		placeholderB.setRef(partB);
		partStack.getChildren().add(placeholderB);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		partService.activate(partA);
		assertEquals(partA, partService.getActivePart());
		partService.bringToTop(partB);
		assertEquals(partB, partService.getActivePart());
	}
	public void testBringToTop_Unrendered() {
		MApplication application = createApplication("partFront", "partBack");
		MWindow window = application.getChildren().get(0);
		MPartStack partStack = (MPartStack) window.getChildren().get(0);
		MPart partFront = (MPart) partStack.getChildren().get(0);
		MPart partBack = (MPart) partStack.getChildren().get(1);
		partBack.setToBeRendered(false);
		partStack.setSelectedElement(partFront);
		window.setSelectedElement(partStack);
		application.setSelectedElement(window);
		initialize(applicationContext, application);
		getEngine().createGui(window);