[mocha-developer] Fwd: Re: Mocha and ActiveRecord

James Mead jamesmead44 at gmail.com
Sat Dec 2 03:54:22 EST 2006

---------- Forwarded message ----------
From: J. B. Rainsberger <jbrains762 at gmail.com>
Date: 02-Dec-2006 02:48
Subject: Re: Mocha and ActiveRecord
To: ruby-talk ML <ruby-talk at ruby-lang.org>

James Mead wrote:
> On 28/11/06, J. B. Rainsberger <jbrains762 at gmail.com> wrote:
>> Suppose I have an Order, which has_many OrderItems. Suppose I want to
>> write a test that checks that when I ask the Order to do something, it
>> asks its order items to do that something. I tried to do this like so:
>> def test_delegates
>>      order_items = []
>>      3.times {
>>          item = mock("order item", :do_something => nil)
>>          order_items.push(item)
>>      }
>>      order = Order.new(:order_items => order_items)
>>      order.do_something
>> end
>> This works with normal objects, but it seems ActiveRecord objects don't
>> like someone passing them Mocha::Mock objects in their constructors.
>> They check that the order items, in this case, are OrderItem objects.
>> Is there something in ActiveRecord I can override to relax this
>> behavior? I don't like having to create an OrderItem just to add a
>> single stub or expectation.
> What we tend to do in this case is stub the collection method itself i.e.
> Order#order_items.
> So you could do something like this...
> def test_should_do_something_to_all_order_items
>  order_items = Array.new(3) { mock('order item', :do_something => nil) }
>  order = Order.new
>  order.stubs(:order_items).returns(order_items)
>  order.do_something
> end
> When I have a spare couple of hours I'll be releasing a new version of
> Mocha
> that supports mocking of the is_a?. This will allow you to make this work
> with ActiveRecord, but with the disadvantage that you are coupling your
> test
> to the innards of ActiveRecord.
> I hope that helps.

That's not bad. I think I'd rather stub the collection than sorry about
is_a?. I'll give this a shot and let you know how it goes.

Thank you, James.
J. B. (Joe) Rainsberger :: http://www.jbrains.ca
Your guide to software craftsmanship
JUnit Recipes: Practical Methods for Programmer Testing
2005 Gordon Pask Award for contribution Agile Software Practice


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