@Override
  public User signUserIn(String username, String password) {
    if (username == null || password == null) {
      throw new RuntimeException("invalid parameter");
    }
    if (users.containsKey(username)) {
      User user = users.get(username);
      if (password.equals(user.getPassword())) {
        return user;
      }
    }
    throw new RuntimeException("User does not exist");
  }
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