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

David Chelimsky dchelimsky at gmail.com
Sun Aug 8 11:53:07 EDT 2010

On Aug 8, 2010, at 10:40 AM, Matt Wynne wrote:
> On 8 Aug 2010, at 16:38, David Chelimsky wrote:
>> On Aug 7, 2010, at 4:10 PM, David Chelimsky wrote:
>>> 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?
>> FYI - here's the issue that spawned this thread: http://github.com/rspec/rspec-rails/issues/152
> Can you use the Assertions module some other way than mixing it into the example (thereby polluting it with the Assertions module's methods?)

I like the idea in the abstract, but most of the rails assertions rely on some state that is local to the example (@response, @controller, @request, etc, etc). RSpec _could_ gather up all those instance variables and pass them into an assertion-wrapper object, but then it would be highly coupled to that implementation and would lead us down a familiar and unfriendly path of forcing rspec-rails releases for every rails release. That's a world I hope to leave behind with Rails 3 :)

It would also eliminate the option to use the Rails assertions directly in examples.

Oh, well :)

> cheers,
> Matt
> http://blog.mattwynne.net
> +44(0)7974 430184

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