Performance design and performance testing are necessarily different from functional test case design. A rigorous test-driven design methodology isn't practical for all performance measurement. A test-first approach to performance provides some advantages in a TDD environment. Experience with applying early performance testing in a TDD framework for a device-driver development project provides insight into the test-first approach. The results show a trend of performance improvement throughout the development life cycle, and better performance compared to an earlier release. Lessons learned include the benefit of having a performance architect on the development team and of tracking performance measurements throughout the development life cycle.This article is part of a special issue on test-driven development.