@VisibleForTesting
    @NonNull
    public IdlingResource getIdlingResource() {
        if (mIdlingResource == null) {
            mIdlingResource = new SimpleIdlingResource();
        }
        return mIdlingResource;
    }
Only called from test, creates and returns a new {@link SimpleIdlingResource}.
ui/espresso/IdlingResourceSample/app/src/main/java/com/example/android/testing/espresso/IdlingResourceSample/MainActivity.java