I looked at the code/documentation for minitest-rails-spec and you can't use `describe` the way you are using it. This section basically explains what's happening:

https://github.com/metaskills/minitest-spec-rails#test-styles

Basically, since it's not mapping Environment to controller/model/helper/mailer, it's not a ActionController/ActiveSupport/ActionMailer/ActionView::TestCase and thus it's not loading the Rails test modules which would allow you to use fixtures. I'd recommend using the subclass style for these tests (which is what that doc also recommends).