[rspec-devel] stub_model

David Chelimsky dchelimsky at gmail.com
Tue Mar 18 09:10:40 EDT 2008

Hi all,

Over the last couple of years I've read a ton of mail from users
concerned with false positives coming from stubbing/mocking methods
that don't exist. I recently added a stub_model method for
rspec_on_rails (not yet released, available in git) which I think
mitigates this a bit. It is still in development and subject to
change, but here's how it works now.

It looks a lot like mock_model.

  stub_model(Person, :name => 'David')

But it works in a fundamentally different way: FIrst, it creates a
real instance (which means you have to create the model to use it). It
assigns it an id by default, but you can set :id => nil if you want it
to behave like a new record. It overrides new_record? so that it
behaves as you would expect (false if there is an id, true if not). It
also overrides #connection, raising an error if there is any attempt
to access the database. This gives you the db isolation you get from
mock_model, but with a real object. Kind of like unit_record, but on
an instance by instance basis.

I've been using this for a few weeks now (just introduced it to the
rspec code base a week or so ago) and I'm finding it very useful. I'm
thinking of changing the generated rails specs to use stub_model
instead of mock_model, and I'd be curious to hear your thoughts about

Also - right now it checks the hash against the model's attributes. If
the model has a matching attribute it gets assigned, otherwise a stub
is created. It occurs to me that, with some modification, this *could*
be used as a bit of an auditing/red-flagging tool. So let's say you do

  stub_model(Person, :attrs => {:last_name => 'Name'}, :stubs =>
{:full_name => 'Full Name'})

In this case it would fail if the Person model changed :last_name to
:given_name, for example. I have very mixed feelings about that, and
might never use it myself, but it would serve to alleviate the fear of
false positives.



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