Cannot use assert_difference and active_support/testing/assertions methods in PORO classes

[allavena]

Using minitest-rails (2.2.0)

When I do a assert_difference, I get a
NoMethodError: undefined methodassert_difference' for #<#<Class:`

The class I am testing is a plain ruby class. It is not inheriting from ActiveRecord::Base, or controller.

All gets fixed if I add to my test_helper.rb

# test_helper.rb
include ActiveSupport::Testing::Assertions

This may be expected behaviour, I don't know.

Classes:

# app/services/my_service.rb
class MyService
# do stuff
end

# test/services/my_service_test.rb
describe MyService do
  it 'should allow assert_difference' do
     assert_difference stuff
  end
end

[blowmage]

The rails assertions are added to ActiveSupport::TestCase. You need to make sure your test is inheriting from AS::TC. You can do this by inheriting from it directly, or if you are sing the spec DSL describe a class that inherits from ActiveRecord. If your class does not inherit from AR, you can use the :model additional description:

describe MyService, :model do
  # tests here
end

[allavena]

Ah, ok. Thanks for the explanation. Expected behaviour then, closing.

[nunosilva800]

This should be documented, I think it's a common use case, for example, to test some POROs defined in lib/ but that rely on fixtures.

@blowmage I can do a PR for this if you think it's worth.