Re: [Simpletest-support] "Mocking" internally called functions/classes

[Noel D. <ma...@mc...>]

On Fri, 22 Aug 2008 06:57:59 +0300
"Kyohere Luke" <pr...@gm...> wrote:

> I'm trying to test Class_A::Method_B(..). Method_B internally calls
> Class_C::Method_D() - which takes a long time, and is accessed from
> the global/autoload mechanism of the application. I'd like to skip
> this call, since it's irrelevant to my tests.

If class_c->method_d() is part of the logic of class_A->method_B()
then it is relevant to the test. Mocking is often a good way to test
object interactions but you could also use the real object. There are
pros and cons to both. I usually favour mocks myself. 

Actually, mocks are more about design than testing (although that too).
If you were coding test-first, you'd have discovered a need for class_C
while writing a test for class_A, mocked it out, and then come back to
implement it later. I can't recommend this way of working strongly
enough. For one thing, you wouldn't be wondering how to test the class
you've just written: it would already be fully-tested ;)

> Aside from re-designing my class/method to read in Class_C as one of
> it's arguments, or else creating a dummy Class_C, and loading it
> before the real one is loaded, is there a way to achieve this with
> Mocks?
You probably should pass it in (either directly or via some kind of
registry/container, as suggested above, and probably in that order of
preference). 

Very often that will be the best choice - but it isn't *always* the
best choice. If class_A should be responsible for instantiating
class_C, the other thing you can do is to use a partial mock:
(1) in class_A, refactor object instantiation into a factory method
(2) knock the method out with a partial mock of class_A
(3) set the method to return a reference to a mock class_C

This is explained in the simplestest docs but I'll post some code if
you're not sure how it works.

> Secondly, is there a way to prevent the class I'm trying to test from
> calling such mundane php functions like file_exists(), etc? Because
> in such a case, I have to design my test to create/delete files from
> the file system and so on.
That's fine. Have a look at
http://aperiplus.sourceforge.net/FileSystemTestCase.php. I've written
some extensions for SimpleTest, and this is what I use for filesystem
tests. It's not really supported and is liable to change suddenly if I
think of something better but it might give you a few ideas. Pinch
anything you like the look of. The expectation classes will work in
a standard UnitTestCase.
http://aperiplus.svn.sourceforge.net/viewvc/aperiplus/lib/simpletest/

Alternatively you could refactor the file_exists() call into a method
and kill it in a partial mock, similar to above. Personally, I'd
just write/unlink the files. In general, when you hit an application
boundary I think that you should use the real resource.


Noel