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
getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		MPart shownPart = partService.showPart("partId", partState);
		assertNotNull(shownPart);
		assertEquals(part, shownPart);
	}
	public void testShowPart_Id_MultipleExists_TrueACTIVATE() {
		testShowPart_Id_MultipleExists(true, PartState.ACTIVATE);
	}
	public void testShowPart_Id_MultipleExists_FalseACTIVATE() {
		testShowPart_Id_MultipleExists(false, PartState.ACTIVATE);
	}
	public void testShowPart_Id_MultipleExists_TrueVISIBLE() {
		testShowPart_Id_MultipleExists(true, PartState.VISIBLE);
	}
	public void testShowPart_Id_MultipleExists_FalseVISIBLE() {
		testShowPart_Id_MultipleExists(false, PartState.VISIBLE);
	}
	public void testShowPart_Id_MultipleExists_TrueCREATE() {
		testShowPart_Id_MultipleExists(true, PartState.CREATE);
	}
	public void testShowPart_Id_MultipleExists_FalseCREATE() {
		testShowPart_Id_MultipleExists(false, PartState.CREATE);
	}
	public void testShowPart_Id_PartInInactivePerspective() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);