message: Tested stack for A -> B
diff: @@ -21,7 +21,7 @@ window.cancelAnimationFrame = () => {};
  describe('NavigationMotion', function () {
  describe('A', function () {
  - it('should render stack', function(){
  + it('should render A', function(){
  var stateNavigator = new StateNavigator([
  { key: 'sceneA' }
  ]);
  @@ -49,8 +49,42 @@ describe('NavigationMotion', function () {
  })
  });
  + describe('A -> B', function () {
  + it('should render [] + B', function(){
  + var stateNavigator = new StateNavigator([
  + { key: 'sceneA' },
  + { key: 'sceneB', trackCrumbTrail: true },
  + ]);
  + stateNavigator.navigate('sceneA');
  + stateNavigator.navigate('sceneB');
  + var {sceneA, sceneB} = stateNavigator.states;
  + var SceneA = () => <div id="sceneA" />;
  + var SceneB = () => <div id="sceneB" />;
  + sceneA.renderScene = () => <SceneA />;
  + sceneB.renderScene = () => <SceneB />;
  + var container = document.createElement('div');
  + ReactDOM.render(
  + <NavigationHandler stateNavigator={stateNavigator}>
  + <NavigationMotion>
  + {(_style, scene, key) => (
  + <div className="scene" key={key}>{scene}</div>
  + )}
  + </NavigationMotion>
  + </NavigationHandler>,
  + container
  + );
  + try {
  + assert.equal(container.querySelectorAll(".scene").length, 2);
  + assert.equal(container.querySelector("#sceneA"), null);
  + assert.notEqual(container.querySelector("#sceneB"), null);
  + } finally {
  + ReactDOM.unmountComponentAtNode(container);
  + }
  + })
  + });
  +
  describe('A to A -> B', function () {
  - it('should render stack', function(){
  + it('should render A + B', function(){
  var stateNavigator = new StateNavigator([
  { key: 'sceneA' },
  { key: 'sceneB', trackCrumbTrail: true },
  