In this article, the author demonstrates how to test a RESTful API built with Yii2 using Codeception. The author provides a step-by-step guide on setting up the test environment, creating test cases for the members and loans endpoints, and running the tests using the composer test-api shortcut. The article highlights the benefits of using Codeception, including its ease of use and ability to write human-readable test cases. The author also shares their experience as a tech enthusiast and software engineer, providing valuable insights into the importance of testing in software development.