Tests try to observe change. But are some systems too big to observe them all? What if we need to test a function with a very complex output? In this talk, we'll explore a Gold Master test– a special test for evaluating complicated legacy systems. We'll look at how this test takes an input, such as a production database, runs it through a transformative function, and then compares the output to an approved version of the output. Testers of every experience level will leave this talk with a new technique for evaluating complex environments, and a broader conception of what a test can be.