Fear, uncertainty and doubt stopping you from playing with shiny new rubies? Not sure that they're exactly the same as the one you're currently using? Let the Small Eigen Collider smash them up and see what they're made of! The Small Eigen Collider uses reflection and metaprogramming to create random Ruby code. The code can be run under different implementations, and the results compared to detect inconsistencies between the versions. So accelerate your Rubies towards the speed of light and see what gets produced. And don't worry about the black holes - the program has created many of them already in the form of segmentation faults!
Zombie-chaser is a graphic(al) interface to mutation testing. Mutation testing involves making modifications to software code, and seeing if the unit tests detect these changes and indicate a failure.
In the zombie-chaser gooey metaphor, mutated code is represented by zombies. Each successful test is represented as the zombies getting one step closer to you, and a failed unit test kills off the zombie. If you fail to kill the zombie, it gets to eat your brains.