Unit testing Room and LiveData

Room calculates the LiveData‘s value lazily when there is an observer.

You can check the sample app.

It uses a getValue utility method which adds an observer to get the value:

public static <T> T getOrAwaitValue(final LiveData<T> liveData) throws InterruptedException {
    final Object[] data = new Object[1];
    final CountDownLatch latch = new CountDownLatch(1);
    Observer<T> observer = new Observer<T>() {
        @Override
        public void onChanged(@Nullable T o) {
            data[0] = o;
            latch.countDown();
            liveData.removeObserver(this);
        }
    };
    liveData.observeForever(observer);
    latch.await(2, TimeUnit.SECONDS);
    //noinspection unchecked
    return (T) data[0];
}

Better w/ kotlin, you can make it an extensions function :).