### Question:
CustomInstallationIdCache { @Nullable public synchronized CustomInstallationIdCacheEntryValue readCacheEntryValue() { JSONObject cidInfo = readCidInfoFromFile(); String cid = cidInfo.optString(CUSTOM_INSTALLATION_ID_KEY, null); String iid = cidInfo.optString(INSTANCE_ID_KEY, null); int status = cidInfo.optInt(CACHE_STATUS_KEY, -1); if (cid == null || iid == null || status == -1) { return null; } return CustomInstallationIdCacheEntryValue.create(cid, iid, CacheStatus.values()[status]); } CustomInstallationIdCache(@NonNull FirebaseApp firebaseApp); @Nullable synchronized CustomInstallationIdCacheEntryValue readCacheEntryValue(); @NonNull synchronized boolean insertOrUpdateCacheEntry(
      @NonNull CustomInstallationIdCacheEntryValue entryValue); @NonNull synchronized boolean clear();  }### Answer:
@Test public void testReadCacheEntry_Null() { assertNull(cache0.readCacheEntryValue()); assertNull(cache1.readCacheEntryValue()); }