Testing is a foundational practice in frontend development, ensuring code quality, catching regressions, and enabling safe refactoring. Two primary types are widely used:

– **Unit Tests:** Test small, isolated pieces of code (like functions or components). They are fast to run and pinpoint failures precisely. Tools like Jest and React Testing Library are commonly used for React component testing.
– **End-to-End (E2E) Tests:** Simulate real user interactions across the entire application, covering UI, API calls, validation, and user feedback. E2E tests verify that the system as a whole works as intended.

**Key Points:**
– Unit and E2E tests complement each other; neither replaces the other.
– E2E tests are slower but catch integration issues that unit tests may miss.
– Not all projects require exhaustive testing—prototypes or MVPs may test only critical paths.

By adopting a balanced testing strategy, teams gain confidence in their codebase, improve documentation, and deliver robust applications.