In this lesson, you completed the final testing of the Create (POST) operation for the CashCard API and encountered an important learning moment regarding how IDs are handled when creating new resources.

Final Testing:

• Tests Passed: Initially, all tests passed, confirming that a new CashCard was successfully created. You used the URI provided in the Location response header to retrieve the newly created resource.

Adding More Assertions:

• To deepen your understanding, you added additional test assertions to verify:

  • The id of the newly created CashCard is not null.
  • The amount matches the value specified during creation (e.g., 250.00).

  assertThat(getResponse.getStatusCode()).isEqualTo(HttpStatus.OK);
  
  DocumentContext documentContext = JsonPath.parse(getResponse.getBody());
  Number id = documentContext.read("$.id");
  Double amount = documentContext.read("$.amount");
  
  assertThat(id).isNotNull();
  assertThat(amount).isEqualTo(250.00);
  

• These assertions confirm that the CashCard was created with the correct amount and that an id was assigned by the database.

Learning Moment:

• Supplying an ID During Creation:

  • You experimented by updating the test to supply an id when creating a new CashCard:

    @Test
    void shouldCreateANewCashCard() {
       CashCard newCashCard = new CashCard(44L, 250.00);
       // ...
    }
    

  • You also modified build.gradle to enable more detailed test logging:

    test {
      testLogging {
        showStandardStreams = true
      }
    }
    

• Test Failure Analysis:

  • Running the tests resulted in a failure with a 500 INTERNAL_SERVER_ERROR status:

    expected: 201 CREATED
     but was: 500 INTERNAL_SERVER_ERROR
    

  • The error message indicated:

    Failed to update entity [CashCard[id=44, amount=250.0]]. Id [44] not found in database.
    

• Understanding the Issue:

  • By supplying an id in the CashCard object, the cashCardRepository.save() method interpreted the operation as an update rather than a create.
  • Since there was no existing CashCard with id 44 in the database, the update operation failed.

Key Takeaways:

• Do Not Supply IDs When Creating New Resources:
  • When creating new CashCard instances, you should not provide an id. The database (via the Repository) is responsible for generating unique IDs.
  • Supplying an id changes the operation from a creation to an update, which can lead to errors if the id does not exist.
• Validation Consideration:
  • Should we validate this requirement in the API?
    • Yes, it is advisable to implement validation in the API to ensure that clients do not supply an id when creating new resources.
    • This can be achieved by checking if an id is present in the incoming CashCard object during a POST request and returning a 400 BAD REQUEST status with an appropriate error message if it is.
    • Implementing such validation improves the robustness of the API and provides clearer guidance to API consumers.

이 레슨에서는 CashCard API의 생성 (POST) 작업에 대한 최종 테스트를 완료하고, 새 리소스를 생성할 때 ID를 어떻게 처리해야 하는지에 대한 중요한 학습 포인트를 발견했습니다.

최종 테스트:

• 테스트 통과: 초기에는 모든 테스트가 성공적으로 통과되어 새로운 CashCard가 성공적으로 생성되었음을 확인했습니다. 응답의 Location 헤더에 제공된 URI를 사용하여 새로 생성된 리소스를 가져왔습니다.

추가 검증 추가:

• 이해를 깊게 하기 위해 추가적인 테스트 단언문을 추가했습니다:

  • 새로 생성된 CashCard의 id가 null이 아님을 확인합니다.
  • amount가 생성 시 지정한 값(예: 250.00)과 일치하는지 확인합니다.

  assertThat(getResponse.getStatusCode()).isEqualTo(HttpStatus.OK);
  
  DocumentContext documentContext = JsonPath.parse(getResponse.getBody());
  Number id = documentContext.read("$.id");
  Double amount = documentContext.read("$.amount");
  
  assertThat(id).isNotNull();
  assertThat(amount).isEqualTo(250.00);
  

• 이 단언문들은 데이터베이스가 id를 할당했고, amount가 정확하게 설정되었음을 확인합니다.