We’ve all seen those codebases that keep us up at night and yet seem impossible to do anything about—especially when it comes to testing. In this talk, I want to share a very practical approach that begins to rapidly gain confidence about your systems and code. The beginning of my approach starts with unit-level tests and system tests. This approach quickly highlights instability while creating confidence with relatively low effort. In one case, this approach stabilized a 6-year old system in less than 2 weeks! When you leave this talk you’ll have a way to approach testing and rescuing some of the toughest codebases in your career.