Clarification: Although TDD requires an initial investment in writing tests, this investment pays off by reducing bugs and improving code quality. In the long run, TDD saves time by reducing the need for extensive debugging.

Practical Example: Developing a REST API for a Customer Management System

Step 1: Test List

For the feature "create and update customer data," the following test scenarios could be identified:

  1. Successful creation of a new customer.
  2. Updating the data of an existing customer.
  3. Error when trying to create a customer without required data.
  4. Error when trying to update a non-existent customer.

Step 2: Write a Test

Let's start with the test for successfully creating a new customer:

@Test
public void testCreateNewCustomerSuccess() {
    CustomerService service = new CustomerService();
    Customer customer = service.createCustomer("Max Mustermann", "max@example.com");
    assertNotNull(customer.getId());
    assertEquals("Max Mustermann", customer.getName());
    assertEquals("max@example.com", customer.getEmail());
}

Step 3: Pass the Test

The implementation of CustomerService and Customer is done in such a way that this test is passed. This forces the development team to think about data validation and handling of customer data from the beginning.

Step 4: Optionally Refactor

After passing the test, we take time to refactor the code. We may realize that the validation logic can be made reusable, or that certain parts of customer management should be outsourced to separate classes.

Step 5: Until the Test List is Empty, Go to Step 2.

We work through the list by writing tests for each scenario, implementing the code to pass the tests, and then refactoring the code as needed. This cyclical approach not only helps to identify errors early but also promotes a thoughtful design and clear structuring of the code.

Time Saving Through Early Error Detection

By applying TDD to the customer management system, the team ensures that all core functionalities work as planned before further code is added. This approach leads to a significant reduction in the time needed for debugging and troubleshooting in later stages of development. The initial investment in writing tests pays off by minimizing future work and ensuring the quality of the software from the outset.

Practical Tips for Getting Started with TDD in API Development

  1. Define Clear Requirements: Make sure you have a clear understanding of the functionalities your API should provide before you start writing the tests.
  2. Start with Core Features: Initially focus on the basic functions of your API and expand them gradually.
  3. Use Mocks and Stubs: For external dependencies or services not yet implemented, mocks and stubs can be useful to isolate and control the test context.

Other myths: