Bug 322368 Sole part in a part stack shown by EPS should be set as the selected element
SSIA
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		MPart part = partService
				.showPart("part", EPartService.PartState.CREATE);
		assertEquals(1, stack.getChildren().size());
		assertEquals(part, stack.getChildren().get(0));
		assertEquals(part, partService.getActivePart());
	}
	public void testShowPart_Id_VISIBLE() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPartStack partStackA = BasicFactoryImpl.eINSTANCE.createPartStack();
		MPartStack partStackB = BasicFactoryImpl.eINSTANCE.createPartStack();
		window.getChildren().add(partStackA);
		window.getChildren().add(partStackB);
		MPart partA1 = BasicFactoryImpl.eINSTANCE.createPart();
		MPart partA2 = BasicFactoryImpl.eINSTANCE.createPart();
		partA1.setElementId("partA1");
		partA2.setElementId("partA2");
		partStackA.getChildren().add(partA1);
		partStackA.getChildren().add(partA2);
		MPart partB1 = BasicFactoryImpl.eINSTANCE.createPart();
		MPart partB2 = BasicFactoryImpl.eINSTANCE.createPart();
		partB1.setElementId("partB1");
		partB2.setElementId("partB2");
		partStackB.getChildren().add(partB1);
		partStackB.getChildren().add(partB2);
		partStackA.setSelectedElement(partA1);