This library support a very simple way to do regression testing in Ruby projects. You write Ruby scripts with samples. Run these and get the sample results as YAML output besides your scripts. Check both the scripts and the YAML files with the results in you Source Code Control System. When you run the scrips on a later (or even previous) version of your code a simple diff show you if and how the changes in your code impact the results of your samples. This is not a replacement for unit testing but a complement: You can produce a lot of samples with a small amount of Ruby code (e.g. a large number of combinations of data).