Bug 334644 Cannot manually un/render a window that's directly under the application
Setting the 'toBeRendered' flag for a window that's a direct child of an application does nothing. The workaround is to manually de/construct it via the IPresentationEngine.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/workbench/PartRenderingEngineTests.java
partSashContainer.getChildren().add(stack);
		window.getChildren().add(partSashContainer);
		application.getChildren().add(window);
		
		MWindow window2 = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window2);
		wb = new E4Workbench(application, appContext);
		wb.createAndRunUI(window);
		IPresentationEngine engine = appContext.get(IPresentationEngine.class);
		engine.createGui(window2);
		
		
		
		EPartService service = (EPartService) window2.getContext().get(
				EPartService.class.getName());
		service.showPart("part", EPartService.PartState.VISIBLE);
		service.showPart("part", EPartService.PartState.CREATE);
		service.showPart("part2", EPartService.PartState.CREATE);
		while (Display.getDefault().readAndDispatch())
			;
	}
	public void testPart_ToBeRendered() {
		MApplication application = ApplicationFactoryImpl.eINSTANCE
				.createApplication();
		application.setContext(appContext);
		appContext.set(MApplication.class.getName(), application);
		MWindow window = BasicFactoryImpl.eINSTANCE.createWindow();
		application.getChildren().add(window);
		MPartStack stack = BasicFactoryImpl.eINSTANCE.createPartStack();
		window.getChildren().add(stack);