lastState.children.forEach((child, index) => {
   if (!NavigationStateUtils.get(nextState, child.key)) {
     nextScenes.push({
       index,
       state: child,
       isStale: true,
     });
   }
 });
 it('can get children', () => {
   var fooState = {key: 'foo'};
   var navState = {children: [{key: 'foobar'}, fooState], index: 0};
   expect(NavigationState.get(navState, 'foo')).toBe(fooState);
   expect(NavigationState.get(navState, 'missing')).toBe(null);
 });