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
partService.activate(partA);
		assertEquals(partA, partService.getActivePart());
		MPart partB = partService.showPart("partB",
				EPartService.PartState.CREATE);
		assertEquals(2, partStack.getChildren().size());
		assertEquals(
				"Only creating the part, the active part should not have changed",
				partA, partService.getActivePart());
		assertNotNull("The shown part should have a context",
				partB.getContext());
		assertFalse(partService.isPartVisible(partB));
	}
	public void testShowPart_Id_CREATE3() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPartDescriptor partDescriptor = org.eclipse.e4.ui.model.application.descriptor.basic.impl.BasicFactoryImpl.eINSTANCE
				.createPartDescriptor();
		partDescriptor.setElementId("partB");
		partDescriptor.setCategory("aCategory");
		application.getDescriptors().add(partDescriptor);
		MPartStack partStackA = BasicFactoryImpl.eINSTANCE.createPartStack();
		window.getChildren().add(partStackA);
		MPartStack partStackB = BasicFactoryImpl.eINSTANCE.createPartStack();
		partStackB.getTags().add("aCategory");
		window.getChildren().add(partStackB);
		MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		partA.setElementId("partA");
		partStackA.getChildren().add(partA);