### Question:
UserInfoManager { public static UserInfoManager getInstance() { if (instance == null) { instance = new UserInfoManager(); } return instance; } private  UserInfoManager(); static UserInfoManager getInstance(); void getUserInfo(String id, Callback<UserInfo> callback); void getUserInfo(ArrayList<String> ids, Callback<@NotNull Map<String, @NotNull UserInfo>> callback); void warmCache(ArrayList<String> ids);  }### Answer:
@Test public void testGetInstance() { String uid = "user"; mFirebaseUser = mock(FirebaseUser.class); when(mFirebaseAuth.getCurrentUser()).thenReturn(mFirebaseUser); when(mFirebaseUser.getUid()).thenReturn(uid); assertNotNull(UserInfoManager.getInstance()); }