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());
		assertNull(partService.createSharedPart("partId"));
	}
	public void testCreateSharedPart_ForceFalse() {
		MApplication application = createApplication(1, new String[1][0]);
		MPartDescriptor partDescriptor = org.eclipse.e4.ui.model.application.descriptor.basic.impl.BasicFactoryImpl.eINSTANCE
				.createPartDescriptor();
		partDescriptor.setElementId("partId");
		application.getDescriptors().add(partDescriptor);
		MWindow window = application.getChildren().get(0);
		getEngine().createGui(window);
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		MPlaceholder placeholderA = partService.createSharedPart("partId",
				false);
		MPlaceholder placeholderB = partService.createSharedPart("partId",
				false);
		assertEquals(1, window.getSharedElements().size());
		MPart part = (MPart) window.getSharedElements().get(0);
		assertEquals(part, placeholderA.getRef());
		assertEquals(part, placeholderB.getRef());
	}
	public void testCreateSharedPart_ForceTrue() {
		MApplication application = createApplication(1, new String[1][0]);
		MPartDescriptor partDescriptor = org.eclipse.e4.ui.model.application.descriptor.basic.impl.BasicFactoryImpl.eINSTANCE
				.createPartDescriptor();
		partDescriptor.setElementId("partId");
		application.getDescriptors().add(partDescriptor);