Test-driven development (TDD) is a software development practice that supposedly leads to better quality and fewer defects in code. TDD is a simple practice, but developers sometimes do not apply all the required steps correctly. This article presents some ofthe most common mistakes that programmers makewhen practicing TDD, identified by an online survey with 218 volunteer programmers. Some mistakes identified were: to forget the refactoring step, building complex test scenarios, and refactor another piece of code while working on a test. Some mistakes are frequently made by around 25% of programmers.