What is this?
I've extracted the test related code from Evil proper, to make it available to package writers. The abstractions are very good and there's frankly no need to re-invent the wheel in order to test your evil-package.
M-x package-install evil-tests
Or you can just put
evil-tests.el somewhere on your load path.
Using in a packge
Follow the ELPA package format and add this to the package header:
;; Package-Requires: ((evil-tests "0.1"))