rspec users - Oct 2009 - Slides from "Uses & Abuses of Mocks & Stubs" at NWRUG

Hi all

I gave a presentation on mock objects this week at the North West Ruby  
User Group in Manchester[1].  I thought some of you may be interested  
in the slides, which are now on my blog[2].

Note that most of the slides were prepared late at night under sleep  
deprivation, so there are a few bits where I had to clear up what I  
meant in response to questions.  (Mainly, by using examples that are  
so trivial it''s not clear what the benefit of a mock object is.)  But  
hopefully there''s enough value in them that non-attendees might find  
them useful.

Feedback gratefully received.

Cheers
Ashley


[1] http://nwrug.org/events/october09/
[2]
http://aviewfromafar.net/2009/10/17/nwrug-slides-uses-and-abuses-of-mocks-and-stubs


-- 
http://www.patchspace.co.uk/
http://www.linkedin.com/in/ashleymoran
http://aviewfromafar.net/

Response written as I go through the slides, and late at night under
sleep deprivation ;)

* 57 juicy slides in half an hour?  Damn dude.
* Not a fan of the "defining an interface" service example.  A single
method named #query that accepts a string that appears to have the
real command is not much of an interface.  What about something like
service.should_receive(:store).with(:first_name => ''Fred'',
:last_name
=> ''Flintstone'') ?
* I dig the be_equivalent_xml_to matcher
* On the Simulating Situations slide I would stub the call to #save
instead of expecting it.  You''re just setting up context for the
example to run in.
* may be a style thing but in your Degrees of Freedom shapes examples
I don''t like creating the shapes in a before. Just inline it
* the shape example where you pass in a mock is really weird to me.
What are you trying to illustrate?  A different example might be more
effective (or I just need to hear the commentary that goes with that
slide)

Over all it looks like a great introduction to the benefits, use, and
pitfalls of mocks.  Thanks for sharing.

Pat

On Sat, Oct 17, 2009 at 12:54 PM, Ashley Moran
<ashley.moran at patchspace.co.uk> wrote:
> Hi all
>
> I gave a presentation on mock objects this week at the North West Ruby User
> Group in Manchester[1]. ?I thought some of you may be interested in the
> slides, which are now on my blog[2].
>
> Note that most of the slides were prepared late at night under sleep
> deprivation, so there are a few bits where I had to clear up what I meant
in
> response to questions. ?(Mainly, by using examples that are so trivial
it''s
> not clear what the benefit of a mock object is.) ?But hopefully
there''s
> enough value in them that non-attendees might find them useful.
>
> Feedback gratefully received.
>
> Cheers
> Ashley
>
>
> [1] http://nwrug.org/events/october09/
> [2]
>
http://aviewfromafar.net/2009/10/17/nwrug-slides-uses-and-abuses-of-mocks-and-stubs
>
>
> --
> http://www.patchspace.co.uk/
> http://www.linkedin.com/in/ashleymoran
> http://aviewfromafar.net/
>
>
>
>
>
>
>
> _______________________________________________
> rspec-users mailing list
> rspec-users at rubyforge.org
> http://rubyforge.org/mailman/listinfo/rspec-users
>

On 21 Oct 2009, at 09:46, Pat Maddox wrote:
> Response written as I go through the slides, and late at night under
> sleep deprivation ;)
Seems fitting, I wrote them under the exact same conditions =)

> * 57 juicy slides in half an hour?  Damn dude.
Well, might have had about 45-50 mins, but there were plenty of  
questions in the middle.  Didn''t have time to prune the slides down  
before the presentation.  I was ready to collapse at the end :)

Would have had longer, but Boxedup.com sponsored free pizza at the bar  
opposite.  So literally before I''d shut my laptop lid, there was a  
mass stampede out of the building...

> * Not a fan of the "defining an interface" service example.  A
single
> method named #query that accepts a string that appears to have the
> real command is not much of an interface.  What about something like
> service.should_receive(:store).with(:first_name =>
''Fred'', :last_name
> => ''Flintstone'') ?
I think you''re right.  Your example is better.

> * I dig the be_equivalent_xml_to matcher
Our implementation is a bit simplistic, but it''s still useful. 
I''ve
put it up as a gist for it[1] in case anyone else finds it useful.

> * On the Simulating Situations slide I would stub the call to #save
> instead of expecting it.  You''re just setting up context for the
> example to run in.
Ah, I just didn''t know off the top of my head how to make a stub  
method raise an error.  You''re right though, it would be much better  
if I had.

> * may be a style thing but in your Degrees of Freedom shapes examples
> I don''t like creating the shapes in a before. Just inline it
It''s funny you say that, when I wrote it I was thinking it was not  
necessary to use a before block, but "that''s the style I
like".  I
almost always separate out the SUT from the examples.  I think it goes  
back to the days when I thought in rigid Given-When-Then terms.

> * the shape example where you pass in a mock is really weird to me.
> What are you trying to illustrate?  A different example might be more
> effective (or I just need to hear the commentary that goes with that
> slide)
Someone else raised an issue with the same slide, so it must really  
suck.  The fact the example is written around a getter should have  
raised an exception in my head (NotEnoughSleepError).  A much better  
example is slide 30 (Hiding Random Behaviour) where @first and @values  
are used in the same manner (to reduce the need to triangulate to  
prove the implementation is not degenerate).

> Over all it looks like a great introduction to the benefits, use, and
> pitfalls of mocks.  Thanks for sharing.
Thanks for the feedback!  It''s the most detailed I''ve had so
far.  If
I repeat the presentation I''ll make all the changes you suggested.   
Except for the liberal use of before blocks :)

Also I should probably add that at the end, when I was reading the  
references, one of the comments I made was along the lines of "I  
finally got round to reading the RSpec Book chapter on mocks the other  
day, and I was really disappointed.  It said everything I was trying  
to, really clearly, and I was tempted to just turn up and read it out  
loud.  So go look at that next."  I daren''t read the rest of the
new
chapters in case it makes the rest of my job redundant =)


Cheers
Ashley


[1] http://gist.github.com/215089


-- 
http://www.patchspace.co.uk/
http://www.linkedin.com/in/ashleymoran
http://aviewfromafar.net/