it { should include foo } fails or provides unexpected output if foo.respond_to?(:description)

[gregates]

This is probably a pretty weird edge case, but here goes:

I have a kind of wrapper object that behaves like this (the details have been abstracted away for hopefully clearer presentation):

class Handler

  def initialize(feature)
    @feature = feature
  end

  def description
    @feature.description
  end
end

Now, it's normally the case that the kind of object passed into @feature responds to :description. But I had a test that looked like this:

describe "::all" do
  subject { Handler.all }

  it { should include Handler.new(Object.new) }
end

This passed when I was using v2.6, but after upgrading to 2.13 it started failing with a NoMethodError: undefined method 'description'. I was surprised by this, because instantiating a Handler should not call the description method. When I tried stubbing the Object.new with a description method that said "This shouldn't be here", I got a passing test that looked like:

FeatureHandler
  ::all
    should include This shouldn't be here

So it appears to me that what's going wrong is that the to_word method in rspec-expectations/lib/rspec/matchers/pretty.rb is using respond_to?(:description) not just to check that the argument responds to :description, but also (implicitly) as a duck-type check -- it's expecting that if the object does respond to :description, we'll have an object of type RSpec::Core::Example or some other rspec object. But obviously that assumption fails in my weird edge case!

I thought about submitting a patch along with this issue report but I'm not really sure what the correct fix is. More explicit type-checking? Differently named methods so that there's even less likelihood of unintended collisions?

[JonRowe]

Can you try 2.14, this has already been worked around.

[JonRowe]

My bad, I was thinking of rspec/rspec-mocks#288 carry on :)