@Override
        public void onRelationshipValidationResult(int relation, Uri origin, boolean result,
                                                   Bundle extras) throws RemoteException {
            TestCustomTabsCallback.this.onRelationshipValidationResult(
                    relation, origin, result, extras);
        }
A test class to check the incoming messages through {@link CustomTabsCallback}.
customtabs/tests/src/android/support/customtabs/TestCustomTabsCallback.java