Test-Driven Development (TDD) is a software development approach where tests are written before the code. This helps to ensure that the code is written to meet the requirements and that it is maintainable and testable. Spring Boot is a popular Java framework that makes it easy to create REST APIs. In this article, we will explore how to use TDD with a Spring Boot REST API.

Set up your project: To get started, create a new Spring Boot project. You can use the Spring Initializr to generate a new project with the necessary dependencies. In this example, we will be using Maven.

Define your API: Next, define the endpoints for your REST API. For example, you may have endpoints for creating, reading, updating, and deleting resources. Define the endpoint URLs, HTTP methods, and request and response payloads.

Write your tests: With your API defined, it’s time to write the tests. Start by writing tests for the endpoint that creates a resource. This will help you define the contract of the endpoint and ensure that it works as expected. Write tests for other endpoints as well.

Implement the code: Once you have written the tests, it’s time to implement the code. Write the code that makes the tests pass. Make sure to keep the code simple and modular.

Refactor: After you have implemented the code, refactor it to make it cleaner and more maintainable. Make sure that the tests still pass after refactoring.

Repeat: Continue writing tests, implementing code, and refactoring until you have implemented all the endpoints for your REST API.

Run integration tests: Once you have implemented all the endpoints, run integration tests to ensure that everything works together as expected. These tests should test the entire system end-to-end.