Rick DeNatale wrote:
On Thu, Jul 23, 2009 at 8:41 PM, Ben Mabey<b...@benmabey.com> wrote:
You can, IMO, use a "mock" like a stub and a "stub" like a
mock.. Take this for example:
describe "#some_method" do
it "delegates to some_obejct" do
some_object = stub('some object', :some_method => "foo")
my_object = MyObject.new(some_object)
my_object.some_method.should == "foo"
end
end
We are using a stub as a dummy object, and yet our expectation is clearing
testing the method call. So is the above a stub or is it really a mock? I
would say that it is acting like a mock. I hope that others on the list
will correct me if I am wrong making this observation/conclusion.
Well, I'm not sure.
There's a difference here.
The stub simply sets things up so that IF some_object receives
:some_method it will return 'foo' instead of something else (including
a method_missing error).
If the implementation looks like:
class MyObject
def initialize(obj)
end
def some_method
"foo"
end
end
Then the stub object proves nothing, the example will succeed whether
it's there or not.
On the other hand using a mock and setting a message expectation
asserts something about the implementation of some_method and it's
relationship to the intialize method. It's more gray-box than
black-box.
True, but I think the difference is very small in this case. In the
delegation example we want to ensure that the other method is called and
that it's return value is returned. Adjusting your implementation
slightly you could still make the message expectation version pass as
well but still be a false-positive:
class MyObject
def initialize(obj)
end
def some_method
some_object.some_method
"foo"
end
end
In both cases another example would be needed to point out the problem- each of which
would rely on returning another canned response. Of course, using triangulation for
something small as delegation is just plain silly. :) FWIW, I would set a message
expectation when specifying delegation. However, to my point if a stub is being used in
this manner I think it is crossing the line of being a dummy object and taking on more of
a "mock"ish like role. Perhaps it is going overboard to say that it is being
used as a mock, but the intent feels the same in this case IMO.
-Ben
_______________________________________________
rspec-users mailing list
rspec-users@rubyforge.org
http://rubyforge.org/mailman/listinfo/rspec-users
