Artifice test pollution: The Lees ran into an issue where every fifth selenium test was failing. They tracked it down to using Artifice to stub responses in their tests. Since Webdriver communicates with the browser through http requests the stubbed Artifice responses were being received by Webdriver, causing unexpected behavior. Be careful stubbing with Artifice or you may accidentally stub all localhost requests.
Devise stretches: Todd found that you can speed up your test suite by turning down Devise’s level of password encryption in your testing environment. He got a 10% bump by including the following code in spec_helper:
Devise.setup do |config| config.stretches = 1 end
For more tips on cutting down your test suite’s run time: