Test-Driven Development

A software development approach where automated tests are written before the code they test, ensuring every feature is designed with testability in mind and has working tests from the moment it is shipped.

Test-driven development catches bugs at the moment of creation rather than after deployment. It forces developers to clarify requirements before writing code and creates a safety net that makes future changes far less risky.

A developer on a founder's team writes a failing test for a new payment calculation feature before writing any code. She then writes the minimum code needed to make the test pass. The result is a feature that is verified to work correctly from day one and protected against future regressions.