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);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		MPlaceholder placeholderA = partService
				.createSharedPart("partId", true);
		MPlaceholder placeholderB = partService
				.createSharedPart("partId", true);
		assertEquals(2, window.getSharedElements().size());
		MPart part1 = (MPart) window.getSharedElements().get(0);
		MPart part2 = (MPart) window.getSharedElements().get(1);
		assertTrue(part1 == placeholderA.getRef()
				|| part1 == placeholderB.getRef());
		assertTrue(part2 == placeholderA.getRef()
				|| part2 == placeholderB.getRef());
	}
	public void testShowPart_Id_ACTIVATE() {
		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();
		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.ACTIVATE);
		assertNotNull(part);
		assertEquals("partId", part.getElementId());
		assertEquals(part, partService.getActivePart());