Can't stub with mocha in ruby on rails test

Question

I'm fairly new to Ruby/Ruby on Rails and having trouble stubbing out a method via mocha in an existing codebase.

I've simplified the code down to a MWE where this breaks.

Here is test_helper.rb:

ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)

require "rails/test_help"


class ActiveSupport::TestCase

end


class Minitest::Test
  def before_setup

  end
end

And here is the test:

require 'test_helper'
require 'mocha/minitest'

class MyTest < ActionMailer::TestCase

  describe "some test" do
    it "should stub" do
      My::Class.stubs(:bar).returns("foo")
      puts My::Class.bar
    end
  end

end

This results in the following error when I run the test:

Mocha::NotInitializedError: Mocha methods cannot be used outside the context of a test

However, when I redefine my test_helper.rb as follows:

ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)

require "rails/test_help"


class ActiveSupport::TestCase

end


# class Minitest::Test
#   def before_setup
#
#   end
# end

The test passes (and "foo" is printed as expected).

Why does the class Minitest::Test...end in test_helper.rb cause the first error? I can't remove that code from the actual codebase, so how can I modify it to work with mocha?

Ruby version: 2.4.1

Rails version: 4.2.8

Mocha version: 1.5.0

How about turning those methods into a module and including it to Minitest::Test? — max pleaner, May 01 '19 at 17:53
@maxpleaner which methods do you mean? Could you elaborate on how to do this? — LateCoder, May 01 '19 at 17:56
Change `class Minitest::Test` to `module MiniTestPatch` and then call `Minitest::Test.include MiniTestPatch` outside the definition. Just worth a shot, I don't know if it will work. — max pleaner, May 01 '19 at 17:57
Actually, you should use `prepend` instead of `include`, and possibly you should be calling `super` in the patched method — max pleaner, May 01 '19 at 18:01
Adding a call to `super` in `before_setup` did the trick - thank you! — LateCoder, May 01 '19 at 18:06

score 2 · Answer 1 · answered May 01 '19 at 18:09

Adding a call to super in the patched method before_setup in test_helper.rb works:

ENV['RAILS_ENV'] ||= 'test'
require File.expand_path('../../config/environment', __FILE__)

require "rails/test_help"


class ActiveSupport::TestCase

end


class Minitest::Test
  def before_setup
      # do something
      super
  end
end

This call to super allows the before_setup of Mocha::Integration::MiniTest to be called, which is necessary for proper initialization.

Can't stub with mocha in ruby on rails test

1 Answers1