@Override
  public void validateUser(User user) {
    if (user == null) {
      throw new IllegalArgumentException("user object cannot be null");
    }
    if (user.getEmail().isEmpty()) {
      throw new RuntimeException("email empty");
    }
    if (user.getUsername().isEmpty()) {
      throw new RuntimeException("username empty");
    }
  }
Just a simple service for handling user registration and sign in.

@author ddary
selendroid-test-app/src/main/java/io/selendroid/testapp/services/impl/UserServiceImpl.java