Unit Testing

Unit Testing isolates and validates the smallest testable code blocks (functions, methods): It ensures each unit performs its specific task correctly, catching approximately 85% of bugs before integration.

Unit Testing is the first-level verification in the development lifecycle: Developers write automated tests to check individual components in isolation, using frameworks like JUnit (Java), NUnit (.NET), or PyTest (Python). This practice ensures a function, for instance, `calculate_discount(price, rate)`, returns the expected output for all inputs, including edge cases. By detecting defects immediately—a 10x cost reduction compared to fixing them in production—the process promotes cleaner, more modular code, facilitates safe refactoring, and significantly strengthens the overall CI/CD pipeline.

https://www.browserstack.com/guide/unit-testing-a-detailed-guide