[Rspec] Difference between stub and message expectation with any_number_of_times

Testing RSpec
1

I’m wondering what’s the difference between stub and message expectation
with any_number_of_times, for example:

myMock = mock(“mymock”)
myMock.stub!(:is_a?).with(MyClass).and_return(false)

and

myMock = mock(“mymock”)
myMock.should_receive(:is_a?).with(MyClass).any_number_of_times.and_return(false)

because is_a? may not be called at all, it just like a stub. Is my
understanding correct?

Is there any guide how to use stub and message expectation?

2

Ok, here is my stab at this:

Since be seem to be only setting and testing bare mocks, I’d assume
this is just useful to pass the mock as a stand in for some other
object. So running a test: [See the code at pastie:
http://pastie.org/1043160
]

I get subtly different messages:

)
Spec::Mocks::MockExpectationError in ‘mocking stub should not be ok if
it gets a at least one good argument and an unexpected argument’
Mock “mymock” received unexpected message :is_a? with (NoMock)
./mock_spec.rb:61:

for stubs

vs.
)
Spec::Mocks::MockExpectationError in ‘mocking mock should see the
incorrect one and report an error’
Mock “mymock” received :is_a? with unexpected arguments
expected: (MyClass)
got: (NoMock)
./mock_spec.rb:28:

for mocks.

The web page says:
"Explicitly Imprecise Counts

my_mock.should_receive(:msg).any_number_of_times
The message can be received 0 or more times.
"

I can’t envision a use case where this is needed, or can’t be emulated
via a stub.

I’d be interested in David C’s take or someone else’s.

Cheers,
Ed

Ed Howland

http://twitter.com/ed_howland

3

On Jul 13, 2010, at 11:29 AM, Benyi W. wrote:

because is_a? may not be called at all, it just like a stub. Is my understanding correct?
Yes.

Is there any guide how to use stub and message expectation?

any_number_of_times was introduced before we introduced stubs, way back,
way back. I use stub() rather than should_receive + any_number_of_times.

HTH,
David