QuickCheck, our testing tool for automatically generating tests, has a long track record of nailing serious and hard-to-find bugs and boosting quality, in software like dets (part of mnesia), Riak, and the embedded software in cars. QuickCheck is written in Erlang and can be used with Elixir, but... can we instrument Elixir code to find race-conditions with PULSE? Not until recently. Now we have an Elixir native interface to access QuickCheck. In this talk, we present QuickCheck and this interface and show how race-conditions can be nailed down.