In the realm of serverless computing, testing emerges as a cornerstone for ensuring the reliability and performance of applications built upon this paradigm. With serverless applications structured as a collection of functions operating in managed environments, effective testing strategies become imperative for identifying and addressing potential issues early in the development lifecycle. In this article, we delve into the comprehensive landscape of testing serverless applications, exploring key approaches such as unit testing, integration testing, and end-to-end testing. Additionally, we discuss essential strategies for mocking external services and dependencies, empowering developers to validate the functionality, reliability, and scalability of their serverless applications with confidence.