API security testing is an essential component of modern software development that focuses on identifying vulnerabilities in API endpoint communication. Automating this testing within a CI/CD pipeline, particularly for Java applications, enhances early vulnerability detection, maintains security standards, and minimizes human errors without impacting development speed. The process involves using tools like OWASP ZAP, Burp Suite, Postman, and REST-Assured, with the latter being particularly beneficial for Java-based projects due to its seamless integration with the Java ecosystem. The tutorial outlines setting up a mock API using WireMock, writing security tests with REST-Assured, and automating these tests with CircleCI to ensure robust API security through various scenarios such as authentication, SQL injection, XSS, CSRF protection, and security headers. The approach not only ensures applications are more secure and reliable but also increases team efficiency by reducing repetitive tasks and enabling swift issue resolution.