The problem was first observed in this mocha CI build failure:

  1) Failure:
LooseKeywordArgumentMatchingTest#test_should_match_hash_parameter_with_keyword_args
[test/acceptance/loose_keyword_argument_matching_test.rb:33]:
Expected nil (NilClass) to respond to #include?.

I have reproduced the problem locally by running the following command in the mocha repo on the ‘main’ branch (097f0addf82c68e7ecdf87ebf5c996d7278fa2a6):

SEED=21038 bundle exec rake test:acceptance

This particular problem doesn't seem to occur when I run the single test or when running all the acceptnace tests with other seed values, so presumably the problem is related to ordering / statefulness between tests. However, I have seen other similar problems with other seed values:

SEED=38546 bundle exec rake test:acceptance

LooseKeywordArgumentMatchingTest#test_should_match_last_positional_hash_with_keyword_args
[test/acceptance/loose_keyword_argument_matching_test.rb:84]:
Expected nil (NilClass) to respond to #include?.

And:

SEED=32553 bundle exec rake test:acceptance

  1) Failure:
StrictKeywordArgumentMatchingTest#test_should_not_match_hash_parameter_with_splatted_keyword_args
[test/acceptance/strict_keyword_argument_matching_test.rb:37]:
Test passed unexpectedly

I think the issue pre-dates JRuby v10.0.2.0, because I see the same failures when running against JRuby v10.0.1.0. I do not see these failures when running against CRuby v3.4.5 or v3.5.0preview1.

I’m happy to investigate this further given that I probably have more knowledge of the internals of the Mocha tests, but it would be helpful to have some understanding of what kind of statefulness there might be in relation to keyword arguments.

I’m tracking this issue in freerange/mocha#760.