Bug 326300 EPartService's activate(MPart) method may not work if you activate the window's active part
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
partStack.setSelectedElement(partFront);
		window.setSelectedElement(partStack);
		application.setSelectedElement(window);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		assertFalse(partBack.isToBeRendered());
		EPartService partService = (EPartService) window.getContext().get(
				EPartService.class.getName());
		partService.activate(partBack);
		assertTrue("Activating a part should cause it to be rendered",
				partBack.isToBeRendered());
	}
	public void testActivate_Focus() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		partA.setContributionURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.application.ClientEditor");
		window.getChildren().add(partA);
		window.setSelectedElement(partA);
		MPart partB = BasicFactoryImpl.eINSTANCE.createPart();
		partB.setContributionURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.application.ClientEditor");
		window.getChildren().add(partB);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		ClientEditor editorB = (ClientEditor) partB.getObject();
		assertFalse(editorB.wasFocusCalled());
		EPartService partService = window.getContext().get(EPartService.class);
		partService.activate(partB);