As pointed here: https://github.com/testing-cabal/mock/issues/353,

this issue is related to the method assert_has_calls or probably any calls that use the method _call_matcher to match calls. Given that you mock a class and spec it, since we always bind to the _spec_signature (e.g. the constructor signature), when it is a method call then it bind() throws a TypeError looking like `missing a require argument`. A possible solution would be to include method signatures into the spec.