[rspec-users] Adding Test Spy into Rspec mocking framework

David Chelimsky dchelimsky at gmail.com
Mon Sep 15 08:54:33 EDT 2008

On Mon, Sep 15, 2008 at 7:18 AM, David Chelimsky <dchelimsky at gmail.com> wrote:
> On Mon, Sep 15, 2008 at 5:09 AM, Joseph Wilk <lists at ruby-forum.com> wrote:
>> Thanks to a pointer from lizkeogh.com site I've been discovering the joy
>> of the Mockito (http://mockito.org/) mocking framework for Java. It
>> verifies behaviour after the action. It struck me how this matched the
>> format I use in my Ruby cucumber features. Within Rspec if we could use
>> post behaviour verifications I could unify the format of my specs with
>> my features. Specs could look like:
>> ---
>> it "should make verfication of behaviour after action"
>>  #Given
>>  setup some mock/stubs
>>  #When
>>  perform action
>>  #Then
>>  Check whether the behaviour was as expected.
>> end
>> ---
>> While we can do this with output checks in Rspec we cannot do such a
>> thing with 'should_receive'.
>> Having a consistent format for specs and stories sounds like a great
>> idea to me.
>> Also the separation of the verification from the Given set-up is nice.
>> So I'm proposing the idea of adding 'should_have_received' and test_spy
>> in Rspec:
>> ---
>> x = test_spy('like a mock but more into espionage')
>> #Action which does not fail on unexpected method but just records calls.
>> some.action(x)
>> x.should_have_received(:method).and_returned_with('some string')
>> ---
>> What I'm still looking at is if the idea of post validation is possible
>> in the Rspec framework mocking framework. I know RR
>> (http://github.com/btakita/rr/tree/master) is looking at implementing
>> the Spy pattern which will enable this sort of testing.
> The main technical problem with this is that RSpec's mocks are
> designed to fail fast, and that would have to be turned off for
> objects intended to simply record calls. It might be that what you're
> talking about should really be a completely separate implementation
> which, I might add, would probably be quite trivial compared to the
> complexities of failing fast in a variety of contexts.
>> Do people think this would be a good addition to Rspec?
> My initial reaction is "no" based on a couple of things:
> 1. Mocks are intended for the indirect discovery of new objects and
> their behaviours while driving out their consumers with code examples.
> If our stories start using them for this purpose, we're heading
> towards what I view is too granular a view from the story level.
> 2. Mocks can get separated from the real implementations, meaning that
> all the code examples can pass yet things can fall apart in production
> if the mocks aren't maintained in alignment with the real
> objects/methods. The risk of using mocks in code examples is
> significantly mitigated with the use of scenarios as integration
> tests. As soon as we start using mocks in stories as well, we're
> reintroducing that risk and likely increasing it.

Just re-read your initial post Joseph - realize that you were not
proposing adding this to stories, so please disregard those concerns.


> Now with all of that said, I think this is worth exploring. I'm just
> not sure that exploration should occur in rspec proper. What I'd
> encourage you to do is write either a standalone library with hooks
> that you can exploit from rspec examples and/or rspec/cucumber
> scenarios or write an extension library for rspec's mocking framework.
> I'd also recommend that everyone interested in this thread read Dan's
> article about endotesting/mockito:
> http://dannorth.net/2008/09/the-end-of-endotesting.
>> ((I'm really excited with the idea and I have started playing around
>> with some code for a prototype. If its not for Rspec I can always look
>> at it for RR.))
> Doesn't RR already support test spy?
>> I've added a issue in lighthouse (though its behaving very strangely at
>> the moment not picking my ticket up in searches/tags)
>> http://rspec.lighthouseapp.com/projects/5645/tickets/527-adding-spy-to-rspecs-mocking-framework
> Thanks for getting this conversation going.
> Cheers,
> David
>> --
>> Joseph Wilk
>> http://www.joesniff.co.uk

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