The tutorial explores the use of xUnit parameterized tests for optimizing Selenium test code by reducing duplication and enhancing code reusability. It highlights how the xUnit framework in C# supports both parameterized and non-parameterized tests, using the Theory attribute to facilitate data-driven testing through attributes like InlineData, ClassData, and MemberData. The tutorial uses LambdaTest, a cloud-based cross-browser testing platform, to demonstrate executing parameterized tests on various browser and operating system combinations, emphasizing the benefits of scalability, parallel execution, and improved test coverage. The guide also discusses the nuances of using InlineData for simple constants, while MemberData and ClassData are recommended for more complex scenarios, illustrating how these approaches can efficiently handle numerous test scenarios in cross-browser testing.