@Test
  public void requestClientRegistrationFail1() throws Exception {
    showTitle("requestClientRegistrationFail1");

    RegisterClient registerClient = new RegisterClient(registrationEndpoint);
    RegisterResponse response = registerClient.execRegister(null, null, null);

    showClient(registerClient);
    assertEquals(response.getStatus(), 400, "Unexpected response code: " + response.getEntity());
    assertNotNull(response.getEntity(), "The entity is null");
    assertNotNull(response.getErrorType(), "The error type is null");
    assertNotNull(response.getErrorDescription(), "The error description is null");
  }
  @Test
  public void requestClientRegistrationFail2() throws Exception {
    showTitle("requestClientRegistrationFail2");

    RegisterClient registerClient = new RegisterClient(registrationEndpoint);
    RegisterResponse response =
        registerClient.execRegister(
            ApplicationType.WEB, "oxAuth test app", null); // Missing redirect URIs

    showClient(registerClient);
    assertEquals(response.getStatus(), 400, "Unexpected response code: " + response.getEntity());
    assertNotNull(response.getEntity(), "The entity is null");
    assertNotNull(response.getErrorType(), "The error type is null");
    assertNotNull(response.getErrorDescription(), "The error description is null");
  }
  @Test
  public void requestClientRegistrationFail3() throws Exception {
    showTitle("requestClientRegistrationFail3");

    RegisterClient registerClient = new RegisterClient(registrationEndpoint);
    RegisterResponse response =
        registerClient.execRegister(
            ApplicationType.WEB,
            "oxAuth test app",
            Arrays.asList("https://client.example.com/cb#fail_fragment"));

    showClient(registerClient);
    assertEquals(response.getStatus(), 400, "Unexpected response code: " + response.getEntity());
    assertNotNull(response.getEntity(), "The entity is null");
    assertNotNull(response.getErrorType(), "The error type is null");
    assertNotNull(response.getErrorDescription(), "The error description is null");
  }