Bug 303218 Active part no longer seems to be queryable from the application's context
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
MPart partFrontB = partStackB.getChildren().get(0);
		MPart partBackB = partStackB.getChildren().get(1);
		partStackB.setSelectedElement(partFrontB);
		windowB.setSelectedElement(partStackB);
		application.setSelectedElement(windowA);
		getEngine().createGui(windowA);
		getEngine().createGui(windowB);
		EPartService partServiceA = (EPartService) partFrontA.getContext().get(
				EPartService.class.getName());
		EPartService partServiceB = (EPartService) partFrontB.getContext().get(
				EPartService.class.getName());
		partServiceA.activate(partBackA);
		assertEquals(partBackA, partServiceA.getActivePart());
		assertFalse(partServiceA.isPartVisible(partFrontA));
		assertTrue(partServiceA.isPartVisible(partBackA));
		assertFalse(partServiceA.isPartVisible(partFrontB));
		assertFalse(partServiceA.isPartVisible(partBackB));
		partServiceA.activate(partBackB);
		assertEquals(partBackA, partServiceA.getActivePart());
		assertFalse(partServiceA.isPartVisible(partFrontA));
		assertTrue(partServiceA.isPartVisible(partBackA));
		assertFalse(partServiceA.isPartVisible(partFrontB));
		assertFalse(partServiceA.isPartVisible(partBackB));
		assertFalse(partServiceB.isPartVisible(partFrontA));
		assertFalse(partServiceB.isPartVisible(partBackA));
		assertTrue(partServiceB.isPartVisible(partFrontB));
		assertFalse(partServiceB.isPartVisible(partBackB));
		partServiceB.activate(partBackB);
		assertEquals(partBackB, partServiceB.getActivePart());
		assertFalse(partServiceB.isPartVisible(partFrontA));