resetForTesting static method
Forgets the initialized preferences so the next init runs again.
Only for tests: SharedPreferences.setMockInitialValues swaps the
platform store, but this class holds a SharedPreferences instance with
its own populated cache, so without this a mocked store from one test is
invisible and the previous test's alarms leak into the next.
Implementation
@visibleForTesting
static void resetForTesting() {
dispose();
_initFuture = null;
}