This slide deck discusses the importance of testing software code. It introduces Jest, a popular JavaScript testing framework, and shows examples of how to test React components. Key points covered include using Jest to test that functions are called correctly, return expected data, and throw proper errors. Snapshots are demonstrated as a way to test that the UI does not change unexpectedly over time. The slide deck concludes by mentioning the importance of end-to-end testing and exploring additional testing techniques.