Unit testing, a critical component of software development, involves testing individual code components independently to ensure quality from the outset. As QA roles expand in DevOps and Agile environments, testers are increasingly tasked with creating unit tests, either directly within the code using tools like JUnit or NUnit or through alternative methods such as black box testing, smoke tests, and API tests. Effective unit testing allows for early detection and resolution of defects, reducing costs associated with fixing issues later in the development cycle. Despite its limitations, such as the inability to identify defects in integrated systems, unit testing contributes significantly to application quality by offering repeatable, isolated tests that can serve as documentation and regression test suites. QA testers need to be versatile, understanding both code-based and alternative unit testing methods to enhance their value in the software development process.