Bug 321757 EPS adds a part without considering its placeholder if target container is not a part stack
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
assertEquals(1, window.getChildren().size());
		assertEquals(part, window.getChildren().get(0));
		assertEquals(part, shownPart);
		assertTrue("A shown part should be rendered", part.isToBeRendered());
	}
	public void testShowPart_Id_Unrendered_CREATE() {
		testShowPart_Id_Unrendered(PartState.CREATE);
	}
	public void testShowPart_Id_Unrendered_VISIBLE() {
		testShowPart_Id_Unrendered(PartState.VISIBLE);
	}
	public void testShowPart_Id_Unrendered_ACTIVATE() {
		testShowPart_Id_Unrendered(PartState.ACTIVATE);
	}
	private void testShowPart_Id_Unrendered2(EPartService.PartState partState) {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		window.setToBeRendered(true);
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPartStack partStack = BasicFactoryImpl.eINSTANCE.createPartStack();
		partStack.setToBeRendered(false);
		window.getChildren().add(partStack);
		window.setSelectedElement(partStack);
		MPart part = BasicFactoryImpl.eINSTANCE.createPart();
		part.setElementId("partId");
		part.setToBeRendered(false);
		partStack.getChildren().add(part);
		partStack.setSelectedElement(part);