minitest - mock - expect keyword arguments

Question

When I want to verify that mock is send expected arguments, I can do

@mock.expect(:fnc, nil, ["a, "b"])

however, if class I want to mock looks like this

class Foo
    def fnc a:, b:
    end
end

how can I mock it and verify values passed as a:, b:?

Answer 1

Below is a real-world example from my company's codebase:

mailer = MiniTest::Mock.new
mailer.expect :deliver, 123 do |template_name:, data:, to:, subject:|
  true
end
mailer.deliver template_name: "xxx", data: {}, to: [], subject: "yyy"

If you also want to verify arguments' types:

mailer.expect :deliver, 123 do |template_name:, data:, to:, subject:|
  template_name.is_a?(String) &&
    data.is_a?(Hash) &&
    to.is_a?(Array) &&
    subject.is_a?(String) &&
end

Update 2022-05-22

You would get ArgumentError if you use this strategy with Ruby v3.

I have submitted a PR here to fix this issue:

https://github.com/minitest/minitest/pull/908

If you wish to use this feature with Ruby v3, please leave some comments to get project owner's attention.

Update 2022-06-28

minitest supports keyword arguments since v5.16.0 🎉

https://github.com/minitest/minitest/blob/master/History.rdoc#5160--2022-06-14-