The Application Program Interface (API) is a set of protocols and tools used to develop and maintain mission-critical software. API testing is crucial to guarantee high-quality applications by regularly checking API functioning in response to API calls and interactions with the system against established input parameters, data formats, error codes, and HTTP status codes. To address security vulnerabilities such as insufficient logging and monitoring, penetration testing and E2E fuzz testing are used to simulate attacks against the API and identify any security flaws and abnormal behaviors. Continuous API testing is recommended throughout the API lifecycle due to the complexity of security vulnerabilities, and it provides several advantages including ensuring software system security, performance, and stability. The decision to build systems as APIs is often a business decision rather than a technology decision, and API testing is now a top priority when developing and deploying APIs. APIs have risen to the forefront of software development as a critical tool for bridging the gap between disparate applications and systems, and comprehensive security testing is necessary to prevent API data breaches.