What is Unit testing?
Unit testing is the practice of writing small automated tests that check individual pieces of code, such as a single function or class, in isolation from the rest of the system. Unit tests run in seconds and pinpoint exactly what broke, while broader tests confirm that the pieces work together.
Why it matters for your business
Good unit test coverage lets developers change code confidently, catches regressions immediately and lowers the cost of maintaining software over its lifetime.
A team writes unit tests for its shipping cost function covering free shipping thresholds and international rates, so a later refactor that breaks one rule fails the build.