### Question:
Settings { public synchronized void clear() { OPFLog.logMethod(); preferences.clear(); } private  Settings(@NonNull final Context context); @SuppressWarnings("PMD.NonThreadSafeSingleton") static Settings getInstance(@NonNull final Context context); @NonNull synchronized State getState(); synchronized void saveState(@NonNull final State state); synchronized void clear(); @Nullable synchronized String getLastProviderName(); synchronized void saveLastProvider(@Nullable final PushProvider provider); @Nullable synchronized String getLastAndroidId(); synchronized void saveLastAndroidId(@Nullable final String androidId); synchronized void saveUnregisteringProvider(@NonNull final String providerName); synchronized void removeUnregisteringProvider(@NonNull final String providerName); synchronized boolean isProviderUnregistrationPerforming(@NonNull final String providerName); synchronized void saveRegisteringProvider(@NonNull final String providerName); synchronized void removeRegisteringProvider(@NonNull final String providerName); synchronized boolean isProviderRegistrationPerforming(@NonNull final String providerName); synchronized void savePendingRegistrationProvider(@NonNull final String providerName); synchronized void removePendingRegistrationProvider(); @Nullable synchronized String getPendingRegistrationProvider(); synchronized void savePendingUnregistrationProvider(@NonNull final String providerName); synchronized void removePendingUnregistrationProvider(); @Nullable synchronized String getPendingUnregistrationProvider();  }### Answer:
@Test public void testClear() { sharedPreferences.edit() .putString(KEY_LAST_PROVIDER_NAME, "not empty") .putInt(KEY_STATE, RND.nextInt()) .putString(KEY_LAST_ANDROID_ID, "string") .apply(); settings.clear(); assertFalse(sharedPreferences.contains(KEY_LAST_PROVIDER_NAME)); assertFalse(sharedPreferences.contains(KEY_STATE)); assertFalse(sharedPreferences.contains(KEY_LAST_ANDROID_ID)); }