FocusManager in FlexUnit4?

I'm trying to write just a simple test ensuring that a TextInput control has focus when a component is loaded. However focusManager is null even after I've used the UIImpersonator class to setup my component. Am I doing it wrong or is this a bug?

UIImpersonator.addChild(sc);

Assert.assertEquals(sc.itemInput.name, Object(sc.focusManager.getFocus()).name);