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
partServiceB.activate(partA);
		assertEquals(0, partListener.getVisible());
		assertEquals(0, partListener.getVisibleParts().size());
		assertTrue(partListener.isValid());
	}
	private void testSavePart(final Save returnValue, boolean confirm,
			boolean beforeDirty, boolean afterDirty, boolean success,
			boolean saveCalled, boolean throwException) {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPart saveablePart = BasicFactoryImpl.eINSTANCE.createPart();
		saveablePart.setDirty(beforeDirty);
		saveablePart
				.setContributionURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.application.ClientEditor");
		window.getChildren().add(saveablePart);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		ClientEditor editor = (ClientEditor) saveablePart.getObject();
		editor.setThrowException(throwException);
		window.getContext().set(ISaveHandler.class.getName(),
				new ISaveHandler() {
					public Save[] promptToSave(Collection<MPart> saveablePart) {
						return null;
					}
					public Save promptToSave(MPart saveablePart) {
						return returnValue;
					}
				});