coreyhaines/rspec-mocks — comment on commit 6fe4168b1abb665ffbf75a2c2220a6fe44b18e2d
File: lib/rspec/mocks/message_expectation.rb line 184
By coreyhaines:

Yeah, yeah. :) Tried to wordsmith it to not need to implement a pluralize method. :) 1 argument, 2 arguments. Ugh!
And, yes, it could be as simple as (["s"]*(arity-1)).uniq.to_s (confusing enough?) HAHA!