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
public void testActivate_Unrendered() {
		MApplication application = createApplication("partFront", "partBack");
		MWindow window = application.getChildren().get(0);
		MPartStack partStack = (MPartStack) window.getChildren().get(0);
		MPart partFront = (MPart) partStack.getChildren().get(0);
		MPart partBack = (MPart) partStack.getChildren().get(1);
		partBack.setToBeRendered(false);
		partStack.setSelectedElement(partFront);
		window.setSelectedElement(partStack);
		application.setSelectedElement(window);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		assertFalse(partBack.isToBeRendered());
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		partService.activate(partBack);
		assertTrue("Activating a part should cause it to be rendered",
				partBack.isToBeRendered());
	}
	public void testActivate_Focus() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		partA.setContributionURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.application.ClientEditor");
		window.getChildren().add(partA);
		window.setSelectedElement(partA);
		MPart partB = BasicFactoryImpl.eINSTANCE.createPart();
		partB.setContributionURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.application.ClientEditor");