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
MWindow window = application.getChildren().get(0);
		MPartDescriptor partDescriptor = org.eclipse.e4.ui.model.application.descriptor.basic.impl.BasicFactoryImpl.eINSTANCE
				.createPartDescriptor();
		partDescriptor.setElementId("partId");
		application.getDescriptors().add(partDescriptor);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		MPart part = partService.showPart("partId", partState);
		assertNotNull(part);
		assertEquals("partId", part.getElementId());
		assertEquals(part, partService.getActivePart());
		MPart part2 = partService.showPart("partId", partState);
		assertEquals("Should not have instantiated a new MPart", part, part2);
		assertEquals(part, partService.getActivePart());
	}
	public void testShowPart_Id_PartAlreadyShown_ACTIVATE() {
		testShowPart_Id_PartAlreadyShown(PartState.ACTIVATE);
	}
	public void testShowPart_Id_PartAlreadyShown_CREATE() {
		testShowPart_Id_PartAlreadyShown(PartState.CREATE);
	}
	public void testShowPart_Id_PartAlreadyShown_VISIBLE() {
		testShowPart_Id_PartAlreadyShown(PartState.VISIBLE);
	}
	private void testShowPart_Id_IncorrectDescriptor(PartState partState) {
		MApplication application = createApplication(1, new String[1][0]);
		MWindow window = application.getChildren().get(0);
		MPartDescriptor partDescriptor = org.eclipse.e4.ui.model.application.descriptor.basic.impl.BasicFactoryImpl.eINSTANCE
				.createPartDescriptor();