Bug 329184 Detached view that is an activation target candidate can prevent perspective switching
1. Detach the 'Outline' view. 2. Window > Open Perspective > Debug 3. Window > Open Perspective > Java 4. The perspective switch doesn't actually happen. You see the 'Debug' perspective's content with an 'Outline' view detached. Closing the 'Outline' view in the 'Debug' perspective will workaround this problem.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
windowService1.getActivePart());
		assertEquals("We activated it just now, this should be active", part,
				windowService2.getActivePart());
	}
	public void testApplicationContextHasActivePart() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		MPart partB = BasicFactoryImpl.eINSTANCE.createPart();
		window.getChildren().add(partA);
		window.getChildren().add(partB);
		window.setSelectedElement(partA);
		
		initialize(applicationContext, application);
		
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		partService.activate(partA);
		Object o = applicationContext.get(IServiceConstants.ACTIVE_PART);
		assertEquals(partA, o);
		partService.activate(partB);
		o = applicationContext.get(IServiceConstants.ACTIVE_PART);
		assertEquals(partB, o);
	}
	private void testShowPart_Bug307747(PartState partState) {
		MApplication application = ApplicationFactoryImpl.eINSTANCE