Jeff Chastain wrote, On 12/21/2006 5:57 PM:
There is always a need for both unit and integration testing, I just don't
like mixing them. Part of test driven development as I understand it is to
write the test for the object, then develop the object.
I'm not sure if you meant this or not, but for clarity's sake, I'll
describe it more like "write a test, then make that test pass." The way
I read what you said above, it sounded like "write all the tests, then
write the class."
How do you do this
if you first have to write the dependent objects?
You don't first have to write the dependent objects. When you find
yourself in need of one, then you create it. But you don't write the
whole thing. Just stub the method you think you need and have it return
what you are expecting - no real code. When you need real code, you
write the test for it first, as you always would.
There is a reason for the
popularity of the mock and stub frameworks in other languages ... it makes
testing more precise.
It can do that, yes. But, I'm not sure if that is why they are
popular. Several "thought leaders" in the Agile movement, as far as
I've been able to ascertain, either don't use them as extensively as
some people do (ie, perhaps they'll only mock database calls so the
tests can still run fast, or interaction with the file system, for
similar reasons), or promote them for use in projects that are are
already well established and have no tests. I haven't seen anyone
recommend them just for testing without dependencies. You still are
depending on the mock, after all.
Yes, you may never run into problems with a dependent
object breaking the object you are testing, but I don't really see that as a
reason to allow the possibility. If it did happen, you could have a long
dependency chain, part of which you might not be able to test (the event
object in Mach-II for example) and debugging would be as difficult as it
would be without unit tests.
I'm not familiar with Mach-II, but I would have thought long dependency
chains are not generally advisable. And I'm certainly no expert on
that, so I could well be wrong. I can't remember a time when I've had
more than 4 or 5 in a chain though. In either case, it is important to
note that if they would be there without the mocks, they will be there
with the mocks too. And still further, if you had been doing what I
attempted to describe, all of it would be under test (that I can see -
but I may certainly have not explained it well enough, or I could be
missing something). The same cannot be said if you are only using
mocks, however.
Can you provide an example, to help me see it?
I have just seen a lot more posts recently about unit tests and TDD, but I
have not seen any examples short of very simple objects with no
dependencies.
Do you have an example you'd like to see in mind? I sat here thinking
of one for a couple of minutes, but I didn't find one in my head. But,
perhaps I can think of one later, if you don't have one in mind.
-Sam
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