Bug 334559 EPartService's part searching path may not include parts outside of the active perspective
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
MPart partA = BasicFactoryImpl.eINSTANCE.createPart();
		perspective.getChildren().add(partA);
		perspective.setSelectedElement(partA);
		MPartStack partStack = BasicFactoryImpl.eINSTANCE.createPartStack();
		perspective.getChildren().add(partStack);
		MPlaceholder placeholderB = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		placeholderB.setRef(partB);
		partB.setCurSharedRef(placeholderB);
		partStack.getChildren().add(placeholderB);
		MPlaceholder placeholderC = AdvancedFactoryImpl.eINSTANCE
				.createPlaceholder();
		placeholderC.setRef(partC);
		partC.setCurSharedRef(placeholderC);
		partStack.getChildren().add(placeholderC);
		partStack.setSelectedElement(placeholderC);
		initialize(applicationContext, application);
		getEngine().createGui(window);
		assertNull(partB.getObject());
		EPartService partService = window.getContext().get(EPartService.class);
		partService.activate(partA);
		partService.hidePart(partA);
		assertEquals(partC, partService.getActivePart());
	}
	public void testHidePart_ActivationHistory19() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		application.setSelectedElement(window);