@UiThreadTest public void testFindCallback() throws Exception { FragmentManager manager = activity.getSupportFragmentManager(); FragmentStack stack = new FragmentStack(activity, manager, CONTAINER_ID); TestFragmentC fragment = new TestFragmentC(); stack.push(fragment); TestFragment2 fragment2 = new TestFragment2(); stack.push(fragment2); assertEquals(fragment, stack.findCallback(fragment2, TestCallback.class)); assertEquals(activity, stack.findCallback(fragment2, Activity.class)); assertNull(stack.findCallback(fragment2, String.class)); }