@Test
  /** Test the useLoginUser method without password */
  public void useLoginUserTest6() {
    Client client = new Client();
    LoginModel loginModel = new LoginModel(client);
    String email = "*****@*****.**";
    String password = null;

    String expected = "no";
    String result = loginModel.useLoginUser(email, password);

    assertEquals(expected, result);
  }
  @Test
  /** Test the useLoginUser method with both email and password wrong */
  public void useLoginUserTest4() {
    Client client = new Client();
    LoginModel loginModel = new LoginModel(client);
    String email = "*****@*****.**";
    String password = "******";

    String expected = "no";
    String result = loginModel.useLoginUser(email, password);

    assertEquals(expected, result);
  }
  @Test
  /** Test the useLoginUser method without */
  public void useLoginUserTest5() {
    Client client = new Client();
    LoginModel loginModel = new LoginModel(client);
    String email = null;
    String password = "******";

    String expected = "no";
    String result = loginModel.useLoginUser(email, password);

    assertEquals(expected, result);
  }
  @Test
  /** Test the useLoginUser method with existed email and password */
  public void useLoginUserTest1() {
    Client client = new Client();
    LoginModel loginModel = new LoginModel(client);
    String email = "*****@*****.**";
    String password = "******";

    String expected = "ok";
    String result = loginModel.useLoginUser(email, password);

    assertEquals(expected, result);
  }