Bug 329310 Part service does not autogenerate stacks if the last container is not one
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
partStack.getChildren().add(placeholderC);
		partStack.setSelectedElement(placeholderC);
		MPlaceholder placeholderA2 = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		placeholderA2.setRef(partA);
		partStack.getChildren().add(placeholderA2);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = window.getContext().get(EPartService.class);
		partService.activate(partA);
		assertEquals(partA, partService.getActivePart());
		partService.switchPerspective(perspectiveB);
		assertEquals(partB, partService.getActivePart());
		partService.activate(partB);
		assertEquals(partB, partService.getActivePart());
		partService.hidePart(partB);
		assertEquals(partC, partService.getActivePart());
	}
	/**
	 * Test to ensure that the active part remains constant between perspective
	 * switches.
	 */
	public void testActivationHistory01() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		window.getSharedElements().add(partA);