Bug 304211 StackRenderer does not set eagerly created controls to the item
Right-clicking on a Java element and then using 'Open Declaration' opens an editor on the specified file but its content is not shown. Switching tabs or selecting items in the 'Outline' view does _not_ help. Seems to be calling IWorkbenchPage's APIs properly. No idea yet as to what's going on over here.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/workbench/PartRenderingEngineTests.java
appContext.set(MApplication.class.getName(), application);
		
		MPartDescriptor descriptor = MApplicationFactory.eINSTANCE
				.createPartDescriptor();
		descriptor
				.setURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.workbench.SampleView");
		descriptor.setId("part");
		descriptor.setCategory("aStack");
		application.getDescriptors().add(descriptor);
		MPartDescriptor descriptor2 = MApplicationFactory.eINSTANCE
				.createPartDescriptor();
		descriptor2
				.setURI("platform:/plugin/org.eclipse.e4.ui.tests/org.eclipse.e4.ui.tests.workbench.SampleView");
		descriptor2.setId("part2");
		descriptor2.setCategory("aStack");
		application.getDescriptors().add(descriptor2);
		
		
		MWindow window = MApplicationFactory.eINSTANCE.createWindow();
		MPartSashContainer partSashContainer = MApplicationFactory.eINSTANCE
				.createPartSashContainer();
		MPartStack stack = MApplicationFactory.eINSTANCE.createPartStack();
		
		stack.setId("aStack");
		partSashContainer.getChildren().add(stack);
		window.getChildren().add(partSashContainer);
		application.getChildren().add(window);
		
		MWindow window2 = MApplicationFactory.eINSTANCE.createWindow();
		application.getChildren().add(window2);