[rspec-users] Testing .Net Newbie

David Chelimsky dchelimsky at gmail.com
Thu Jan 14 07:15:23 EST 2010


On Thu, Jan 14, 2010 at 5:46 AM, John Polling <lists at ruby-forum.com> wrote:

> Hi,
>
> I've been a .Net developer for a number of years now and I'm a big fan
> of TDD / BDD.  I have been following these principles for a couple of
> years and use tools such as NUnit for testing purposes.
>
> I am now looking at moving across to using RoR for a number of projects
> and I'm still getting my head around how everything works.  I've been
> reading up on RSpec and Cucumber and I have one question looming in my
> head.  (This may be my .Net head messing things up for me).
>
> Normally in .Net when TDDing a controller class I would mock out other
> library classes that the controller calls, such as Repository layer
> classes.  However I notice when using Cucumber people _very_ rarely mock
> anything and I'm assuming this is because Cucumber is meant for testing
> the full stack (Integration testing).


Cucumber is intended for Acceptance Testing. The entry point into the system
can vary. With Rails you can go through the browser (driving Selenium,
Watir, etc from Cucumber), start at the router, or even go directly to the
model in cases where that's appropriate.

re: Integration testing, everybody has a different definition. Before Rails
came along, the prevalent definition that I was aware of was "testing the
behaviour of two non-trivial components together."

More recently, the definition that makes most sense to me comes from Growing
Object Oriented Software [1]. I don't have the book in front of me, but from
memory it is something like "testing your code with other code that you
don't have any control over." Because we need a database for all levels of
Rails testing, this suggests that all Rails testing is Integration Testing.

In Rails' terminology, however, "integration testing" means very
specifically testing the full stack minus the browser.


> I'd normally do this with something like Selenium in .Net.
>

> My question is, when creating a controller (or other class) that relies
> on other library classes is it best to just use RSpec rather than
> Cucumber to mock out the other dependencies and then bring in Cucumber
> scenarios later when you know your RSpec tests are passing?
>

"is it best?" is always relative. YMMV. That said, the outside-in process of
BDD using Cucumber and RSpec together works well like this (borrowed and
modified from the 2nd post in
http://groups.google.com/group/cukes/browse_thread/thread/2598d6fcd29bfd86):

1) Identify business need (the very outside)
2) Discuss what feature would solve this need (feature injection)
3) Write a Cucumber scenario that interacts with the system boundaries (that
have yet to be written)
4) Run the scenario and watch it fail because the code doesn't exist yet
5) Write a little piece of the system boundary code that was missing and
caused the test to fail
6) Run the scenario and watch it fail again, this time because the
code doesn't do what it needs to yet
7) Write a code example in RSpec
8) Run the code example and watch it fail
9) Write enough code to make it pass
10) Run the scenario and check its status
11) Repeat 7-10 until you have enough code (and not more than just enough)
to make the scenario pass.

One catch-phrase that comes to mind is "use Cucumber to learn what code to
write, use RSpec to write the right code."

You should know that there is a trend these days among Cucumber/RSpec/Rails
users to _not_ write controller specs on the basis that controllers are
covered by the Cucumber scenarios. The benefit is a faster suite that
appears to have less duplication between testing layers. The drawback is
that you lose the benefit of discovering model interfaces when you're
specifying the controllers in isolation.

My view is that this makes sense for the boilerplate stuff, but
customizations of the controller are well served with isolated specs in
RSpec.

More answer than you bargained for, I imagine.

HTH,
David

[1]
http://www.amazon.com/Growing-Object-Oriented-Software-Guided-Tests/dp/0321503627


>
> Thanks
>
> John
> --
> Posted via http://www.ruby-forum.com/.
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