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
stack.getChildren().add(part);
		stack.setSelectedElement(part);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		window.getContext().get(EPartService.class).hidePart(part, force);
		assertNull(stack.getSelectedElement());
	}
	public void testHidePart_Bug327044_True() {
		testHidePart_Bug327044(true);
	}
	public void testHidePart_Bug327044_False() {
		testHidePart_Bug327044(false);
	}
	private void testHidePart_Bug327765(boolean force) {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);
		MPart part = BasicFactoryImpl.eINSTANCE.createPart();
		window.getSharedElements().add(part);
		MPerspectiveStack perspectiveStack = AdvancedFactoryImpl.eINSTANCE
				.createPerspectiveStack();
		window.getChildren().add(perspectiveStack);
		window.setSelectedElement(perspectiveStack);
		MPerspective perspectiveA = AdvancedFactoryImpl.eINSTANCE
				.createPerspective();
		perspectiveStack.getChildren().add(perspectiveA);
		perspectiveStack.setSelectedElement(perspectiveA);
		MPlaceholder placeholderA = AdvancedFactoryImpl.eINSTANCE