Mozilla Firefox, holding a significant position in the browser market, mandates its inclusion in Selenium testing to ensure comprehensive cross-browser test coverage. The Selenium FirefoxDriver, or Geckodriver, acts as a proxy for executing Selenium tests on Firefox, using a JSON wire protocol to communicate instructions. This tutorial guides users through downloading and setting up the FirefoxDriver, implementing it in Selenium projects using various programming languages, and utilizing it with the NUnit framework for C# testing. It emphasizes the importance of incorporating FirefoxDriver in testing scripts due to Firefox's market presence and discusses the benefits of using cloud-based services like LambdaTest for broader test coverage. The article illustrates executing test cases on LambdaTest’s cloud platform, enabling tests across various browser versions and operating systems, thereby enhancing testing efficiency and effectiveness without the need for extensive in-house infrastructure.