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
MPlaceholder areaPlaceholderB = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		areaPlaceholderB.setRef(area);
		perspectiveB.getChildren().add(areaPlaceholderB);
		perspectiveB.setSelectedElement(areaPlaceholderB);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		EPartService partService = window.getContext().get(EPartService.class);
		partService.activate(partA);
		partService.switchPerspective(perspectiveB);
		partService.hidePart(partA);
		partService.switchPerspective(perspectiveA);
		assertEquals(partC, partService.getActivePart());
	}
	private MApplication createApplication(String partId) {
		return createApplication(new String[] { partId });
	}
	private MApplication createApplication(String... partIds) {
		return createApplication(new String[][] { partIds });
	}
	private MApplication createApplication(String[]... partIds) {
		return createApplication(partIds.length, partIds);
	}
	private MApplication createApplication(int windows, String[][] partIds) {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		for (int i = 0; i < windows; i++) {
			MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
			application.getChildren().add(window);
			MPartStack partStack = BasicFactoryImpl.eINSTANCE.createPartStack();