Front-end development, particularly UI code, has historically been challenging to test due to its vulnerability to bugs from factors like API inconsistencies and user input variability. However, with the advent of React and its ecosystem of testing tools, developers can now create reliable tests that ensure code correctness. In modern JavaScript front ends, testing is typically divided into three categories: unit tests, which focus on individual components; application tests (or integration tests), which assess entire application logic often with mocked APIs; and end-to-end tests, which validate the complete system, including front-end and back-end interactions. The article delves into unit testing in React, categorized into logic tests, component tests, and Storybook tests, using tools like Jest, Mocha, and Enzyme. It emphasizes the importance of writing tests based on component complexity, likelihood of change, and robustness requirements, suggesting that unit tests can reduce bugs over time and assist in component development. It concludes with a nod to additional resources and tools like LogRocket for tracking errors in React applications.