From theniels at gmail.com  Fri May  2 09:35:28 2008
From: theniels at gmail.com (Niels Bergsland)
Date: Fri, 2 May 2008 09:35:28 -0400
Subject: [Flexmock-users] Partial mock on a rails class
Message-ID: <a7ed9310805020635ra9df49ai5ff3afb4ffdfb19@mail.gmail.com>

Hi flexmock users,
A coworker of mine and I have been using flexmock (and have been very
happy with it!) and ran into a strange issue last night when partial
mocking one of our rails classes.

We have AnalysisFile objects which belong to an Analysis.  All of our
Analysis objects currently belong to one of two different types of
objects.  Both of those objects implement a method called subject
which returns a Subject object.  As a convenience method, we added the
subject method to AnalysisFile.  The code is as follows:

class AnalysisFile
  belongs_to :analysis
  #snipped
  def subject
    owner = self.analysis.owner
    unless owner.respond_to?(:subject)
      raise RuntimeError.new(
          'Owner does not know about any owning subject.')
    end
    return owner.subject
  end
  #snipped
 end

We wanted to use flexmock to test the part of the code that raises the
RuntimeError.

Our original idea was to do the following:

def test_find_subject

   analysis_file = analyses_files(:fll_roi)
   analysis = analysis_file.analysis
   mock_analysis = flexmock(analysis)
   mock_analysis.should_receive(:owner).and_return(1)
   analysis_file.analysis = mock_analysis
   assert_raise(RuntimeError) do
     analysis_file.subject
   end

end

Unfortunately, this did not work as it resulted in:

NoMethodError: You have a nil object when you didn't expect it!
The error occurred while evaluating nil.should_receive
    /usr/local/lib/ruby/gems/1.8/gems/flexmock-0.8.0/lib/flexmock/partial_mock.rb:95:in
`should_receive'
    analysis_file_test.rb:50:in `test_find_subject'

Interestingly though (at least to us!) was that if we changed

mock_analysis = flexmock(analysis)

to

mock_analysis = flexmock(analysis.reload)

The test worked fine!  We thought it was something with the way Rails
lazy loads objects from the database.  But calling other methods on
analysis before flexmock(analysis), to effectively force loading from
the database, still resulted in the NoMethodError.

Are we doing something fundamentally wrong and that calling reload is
causing the test to work by coincidence?
Thanks for any insight!

-Niels