This tutorial guides readers through creating a new Symfony application to manage customer details while emphasizing the importance of testing in software development. By outlining the process of setting up a Symfony project and implementing basic functionalities, such as creating a controller and entity class, the text illustrates how to write unit and functional tests using PHPUnit. It also covers how to automate these tests with CircleCI, ensuring that once code is pushed to GitHub, tests run automatically, facilitating continuous integration. The tutorial highlights Symfony's robust framework, PHPUnit's role in testing, and CircleCI's capabilities in automating the testing process, providing foundational knowledge for developers to create more reliable applications.