Bug 322403 Showing a shared part with PartState.VISIBLE may not work correctly due to incorrect parent comparisons
We check the parents of the active part against the part-to-be-shown to determine how to respond when PartState.VISIBLE is used but the check is always 'true' for shared parts because getParent() returns 'null' for both parts. This is obviously wrong. We need to update the code to consider placeholders.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
MPartStack partStackB = BasicFactoryImpl.eINSTANCE.createPartStack();
		partStackB.getTags().add("aCategory");
		window.getChildren().add(partStackB);
		MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		partA.setElementId("partA");
		partStackA.getChildren().add(partA);
		partStackA.setSelectedElement(partA);
		window.setSelectedElement(partStackA);
		application.setSelectedElement(window);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		partService.activate(partA);
		assertEquals(partA, partService.getActivePart());
		MPart partB = partService.showPart("partB",
				EPartService.PartState.CREATE);
		assertEquals(1, partStackA.getChildren().size());
		assertEquals(
				"Only creating the part, the active part should not have changed",
				partA, partService.getActivePart());
		assertNotNull("The shown part should have a context",
				partB.getContext());
		assertTrue(
				"The part is the only one in the stack, it should be visible",
				partService.isPartVisible(partB));
	}
	public void testShowPart_Id_CREATE4() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();