From: Trans <transfire@...>
Date: 2005-10-29T01:27:04+09:00
Subject: Re: Cut-based AOP


Ed Howland wrote:
>
> No problem, just something I've been thinking about. Brian Button (and
> others,) have said in testing, don't test the disk, and don't test the
> I/O subsystem, don't test the OS, and don't test the built-in std
> library. So, if the application is supposed to do these things, then
> they are hard to test. Which has given rise to many diverse ways of
> addressing this via mocking, using interfaces, dependancy injection
> and so forth.

Which reminds me, I have some tests that are doing this that I need to
fix.

> Ruby is nice, because you can mess about with its innards, and thus
> get around some of these difficulties. Although, with TDDing and
> refactoring, you shouldn't paint yourself into corners in the first
> place. But for legacy code, this approach has some merit, IMO.
>
> AOP strategies for unit testing are nothing new:
> http://blogs.codehaus.org/people/vmassol/archives/000138_aop_unit_testing_example.html
>
> Another potential use of AOP with testing is in fault injection:
>
> cut IMHacker < Kernel
>    def exec(command, *args)
>        raise SecurityError "Caught ya, you lazy good-fer-nuthing low-life"
>        ...
>    end
> end

LOL :)

IOn this case though Kernel is module, so you can't cut it (cause you
can't sublcass it) But of course you could cut Object or use a module
and preclude:

module IMHacker
   def exec(command, *args)
       raise SecurityError "Caught ya, you lazy good-fer-nuthing
low-life"
       ...
   end
end
Kernel.preclude IMhacker

> def test_catchem
>      assert_raise(SecurityError) { exec("cat /etc/passwd") }
> end
>
> .. where the exec call would really be buried in another class somewhere.
>
> Any is there any prototypes of this available anywhere, or is it too
> soon to ask that yet?

Yes, though it doesn't do everything mentioned in the RCR, but it does
the basics:

  http://rubyforge.org/frs/?group_id=137

> I'd vote for this, but RCRchive won't let me in.

Thanks. We've got a good favorable margin so it's okay, but I hope you
find out what's wrong.

T.