Learn how to test a Next.js application using React Testing Library and Jest in this comprehensive tutorial video. Explore the differences between unit testing and integration testing, and discover how to implement both in a Next.js environment. Gain hands-on experience writing unit tests for various components, including Nav, Header, TodoItem, TodoList, and AddTodo. Dive into integration testing for the entire application and understand the nuances of testing in Next.js 13. Master essential concepts such as Testing Library query types and proper test folder organization. Follow along with practical examples and gain valuable insights to enhance your web development skills and create more robust Next.js applications.