I’m currently extracting a plugin used in a Spina CMS site into a reusable module. And since it relies on a relation to an existing class in Spina, fixtures become a nightmare (since it relies on the users, and there’s no easy way to set password digests using fixtures).

Enter FactoryBot (formerly FactoryGirl).

Unfortunately, even after following all the steps to install it, I kept getting the following error:

ArgumentError: Factory not registered: post

No luck searching for an answer. Plenty for it not working with RSpec or some other setup, but nothing with Minitest.

Thankfully, you can load FactoryBot in the console… (I’ve replaced the full path to the gem to ... here readability.)

>  FactoryBot.find_definitions
=> [".../test/dummy/factories", ".../test/dummy/test/factories", ".../test/dummy/spec/factories"]

Wait. That’s not right. Except it sort of is. If you run Rails.root in your console, you’ll see that it is actually test/dummy from your gem. So our factories simply aren’t where FactoryBot is expecting them.

Add the following line into test_helper.rb, just above the FactoryBot.find_definitions line:

FactoryBot.definition_file_paths << File.expand_path('../factories', __FILE__)

That puts the test/factories directory of your gem into the load path. Suddenly everything is working. Well, the tests are failing in the expected manner, at least.