Test Doubles - Verifying Expectations with Spies

This topic is for the [Verifying Expectations with Spies][] exercise in the [Test Doubles][] trail. Post any questions, corrections, or pointers you have to share with other Upcase subscribers.
[Verifying Expectations with Spies]: https://exercises.upcase.com/exercises/verifying-expectations-with-spies
[Test Doubles]: https://thoughtbot.com/upcase/test-doubles