Mocha::StateMachine states method stomps on states fixture about mocha HOT 8 CLOSED

Thank you for the quick response and from saving me to having to dig into the Rails source. Will try the suggested workarounds. Will close the issue -- because this clearly not a mocha problem.

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Hmm. Mocha has implemented the Mocha::API#states method for many years, so something must've changed in Rails. I'm not very familiar with fixtures these days, but it looks as if Rails must be magically defining a #states method and somehow making that available from within the tests. I'm guessing that in Rails v7.0.8 this was happening after require 'mocha/minitest', but in Rails v7.1.1 it's happening before this point.

Looking into it a bit more, this Rails PR which was included in Rails v7.1.0.beta1 looks very suspicious. It looks like it's changed from defining the fixture accessor methods up-front to relying on a method_missing implementation and presumably Mocha::API#states is intercepting the relevant calls.

I can't immediate think of a nice way around this. Perhaps you could rename the fixture accessor somehow, e.g. rename the YML file to e.g. my_states.yml and either use model_class within the YML or ActiveRecord::TestFixtures::ClassMethods#set_fixture_class in the test to specify the model class as State...?

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Another option might be to define another #states method in the relevant test to "override" Mocha::API#states and then call the fixture accessor via #method_missing, e.g.

require 'test_helper'

class StateTest < ActiveSupport::TestCase
  fixtures :states
  it 'returns #abbreviation - #name' do
    assert_equal 'RB - Robonia', states(:robonia).display_name
  end

  private
  def states
    method_missing(:states)
  end
end

I haven't actually tried this so YMMV!

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Thank you for the quick response and from saving me to having to dig into the Rails source.

No worries - I hope that was the relevant change!

Will try the suggested workarounds.

Good luck! 🤞 Let me know if they work!

Will close the issue -- because this clearly not a mocha problem.

Thanks. I think one could argue that Mocha shouldn't add a method with such a common name to the test context, but given this is the first time I've heard about this being a problem, I'm not planning to make a change at this stage.

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Confess, I simply stopped using the :states fixture in the first repo. But, while bumping another app where the State class has some more meat, I had to actually implement a workaround.

1. renamed states.yml -> us_states.yml
2. added set_fixture_class(us_states: State) to class ActiveSupport::TestCase
3. renamed all references to the :states fixture to :us_states

let(:ct) { us_states(:CT) }

And we're green again.

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@DBugger32 Cool! Thanks for letting me know! 👍

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Just ran into this today. I'm only planning on accessing my states fixtures from my system tests so was able to patch like this:

❯ git diff
diff --git a/test/application_system_test_case.rb b/test/application_system_test_case.rb
index 5960411..6645a24 100644
--- a/test/application_system_test_case.rb
+++ b/test/application_system_test_case.rb
@@ -1,3 +1,8 @@
 class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
   driven_by :selenium, using: :headless_chrome
+
+  def states(...)
+    # https://github.com/freerange/mocha/issues/620
+    access_fixture("states", ...)
+  end
 end

And then have my system tests inherit from ApplicationSystemTestCase

This is good enough for me because I don't plan to use Mocha's state machine API. But wanted to add a data point to this conversation.

FWIW, my states fixtures represent a collection of US states.

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@josefarias Thanks for posting this. I'm not sure there's much more Mocha can do about this. Since Rails is now relying on method_missing, I think perhaps Rails should include a check that the method hasn't already been defined. I'll give this some more thought.

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