rspec users - Aug 2011 - What causes "undefined method `each_pair'"?

Hey folks. I''ve been running into this problem a lot lately, and
haven''t
been able to figure out what''s causing it, nor how to fix it:

Failure/Error: @importer = SpreadsheetImporter.new @catalog, @excel, 
@photos_dir
NoMethodError:
  undefined method `each_pair'' for #<Catalog:0xb885f08>
# ./app/models/spreadsheet_importer.rb:15:in `initialize''
# ./spec/models/spreadsheet_importer_spec.rb:25:in `new''
# ./spec/models/spreadsheet_importer_spec.rb:25:in `block (2 levels) in <top 
(required)>''

Line 15 of spreadsheet_importer.rb is:
@products_importer  = SpreadsheetImporter::Products.new catalog, spreadsheet

Line 25 of spreadsheet_importer_spec.rb is:
@importer = SpreadsheetImporter.new @catalog, @excel, @photos_dir

What perplexes me is that I''ve stubbed out the call to 
SpreadsheetImporter::Products.new , so the class'' initializer
isn''t being
called.

Here''re some more complete code snippets:
https://gist.github.com/1178636

Any help would be greatly appreciated. Thanks!
Nick
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On Sep 3, 2011, at 5:29 AM, Katrina Owen wrote:
> Hi,
> 
> On Mon, Aug 29, 2011 at 5:33 PM, Nick <nick at deadorange.com> wrote:
>> Hey folks. I''ve been running into this problem a lot lately,
and haven''t
>> been able to figure out what''s causing it, nor how to fix it:
>> Failure/Error: @importer = SpreadsheetImporter.new @catalog, @excel,
>> @photos_dir
>> NoMethodError:
>>   undefined method `each_pair'' for #<Catalog:0xb885f08>
>> # ./app/models/spreadsheet_importer.rb:15:in `initialize''
>> # ./spec/models/spreadsheet_importer_spec.rb:25:in `new''
>> # ./spec/models/spreadsheet_importer_spec.rb:25:in `block (2 levels) in
<top
>> (required)>''
>> Line 15 of spreadsheet_importer.rb is:
>> @products_importer  = SpreadsheetImporter::Products.new catalog,
spreadsheet
>> 
>> Line 25 of spreadsheet_importer_spec.rb is:
>> @importer = SpreadsheetImporter.new @catalog, @excel, @photos_dir
>> 
>> What perplexes me is that I''ve stubbed out the call to
>> SpreadsheetImporter::Products.new , so the class'' initializer
isn''t being
>> called.
>> Here''re some more complete code snippets:
>> https://gist.github.com/1178636
> 
> 
> In your gist, the describe block doesn''t contain an "it"
or "specify"
> block. Only a before(:each).
@Katrina - actually it does contain an example ("it") in the nested
group ("describe"). There''s just no example in the outer
group, but that''s a red herring vis a vis this issue.

@Nick - the backtrace tells you the whole story. You just have to look at it.

The problem is that caused when rspec-mocks is asking the incoming Catalog
object if it is == to the expected @catalog (as declared in the
''with'' clause). rspec-mocks has a feature that allows you to
check against a matcher object (i.e.
foo.should_receive(:bar).with(hash_including(:a => ''b''))).
This is implemented in
https://github.com/rspec/rspec-mocks/blob/v2.5.0/lib/rspec/mocks/argument_expectation.rb.
rspec-mocks incorrectly thinks the @catalog is a matcher because it responds to
:matches? and :description (see
https://github.com/rspec/rspec-mocks/blob/v2.5.0/lib/rspec/mocks/argument_expectation.rb#L29),
and therefore wraps it in a MatcherMatcher
(https://github.com/rspec/rspec-mocks/blob/v2.5.0/lib/rspec/mocks/argument_matchers.rb#L101-109),
which asks the @catalog if it matches? the incoming catalog, which mixes in the
Mongoid::Matchers module
(https://github.com/mongoid/mongoid/blob/c4675a987925a831dc93ab5c525c99dedf46c841/lib/mongoid/matchers.rb#L19-30).
That''s how we get to `each_pair` on the Catalog.

So the bug is that rspec''s definition of what a matcher is is too loose
in this case. The problem is that this is RSpec''s API for argument
matching. If we were to make it more strict now, we''d break unknown
numbers of existing specs.

To get around this, you can do this:

SpreadsheetImporter::Products.stub(:new) do |catalog, excel|
  catalog.should eq(@catalog)
  excel.should eq(@excel)
  @products_importer
end

This has the same effect as what you are trying to do (stub
SpreadsheetImporter::Products returning @products_importer, and verify the
arguments are the right ones).

HTH,
David
> Not sure if that''s what''s causing it, but it would be a
place to start.
> 
> Katrina
> 
>> Any help would be greatly appreciated. Thanks!
>> Nick
> 
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