[rspec-users] Name collision - how would you handle this?

David Chelimsky dchelimsky at gmail.com
Sat Aug 7 17:10:03 EDT 2010

Hey all,

It turns out that if you have

* Rails (2 or 3)
* Ruby-1.9
* a model named Message
* let(:message) or def message in an example group
* a Rails assertion in an example in that group
  * note that rspec-rails' matchers delegate to Rails' assertions

You'll get an error saying "wrong number of arguments (1 for 0)"

This is because the rails assertion, which, when running with Ruby-1.9, delegates to Minitest::Assertions#assert_block, which delegates to a message() method that it defines. So the message() method defined by let() overrides the message() method in the Assertions module, and results in unexpected and undesirable outcomes.

So - what should we do? I don't think changing Minitest is really an option, as too many assertion libraries already wrap Minitest assertions. I don't think RSpec should be in the business of monitoring methods end-users define to make sure they're not overriding pre-existing methods (what if you override a method intentionally?). The only thing I'm left with is document this particular case and hope for the best, but that feels unsatisfactory as well.

Recommendations? Words of wisdom?


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