From: Daniel Berger <djberg96@...>
Date: 2006-11-25T09:30:08+09:00
Subject: Re: Generic way to test for expected SystemCallError


Stefano Crocco wrote:
> Daniel Berger wrote:
> > Hi all,
> >
> > Ruby 1.8.x
> >
> > I've got a few tests where I'm looking for expected errors.  These are
> > various system call errors.  The problem is that the exact Errno is
> > different from platform to platform, so I end up writing stuff like
> > this:
> >
> > assert_raises(Errno::EACCES, Errno::ENOTEMPTY){ Dir.unlink('some_dir')
> > }
> >
> > This isn't very robust, since a new platform might fail with a
> > different kind of Errno.  What I would like is a way to have this test
> > succeed:
> >
> > assert_raises(SystemCallError){ Dir.unlink('some_dir') }
> >
> > The problem is that assert_raises looks for a specific error class.  Is
> > there a way to tell TestUnit to expect any error that's a subclass of
> > SystemCallError?
> >
> > Thanks,
> >
> > Dan
> >
> > PS - I see from the documentation that assert_raise is deprecated in
> > 1.9.  What's replacing it?
>
> The simplest way to do this which comes to my mind is to use the fact that the
> exceptions you need are the only constants in the Errno module. This allows
> you to write
>
>   assert_raise(*(Errno.constants.map{|c| Errno.const_get(c)}))
> {Dir.unlink('some_dir')}
>
> Errno.constants gives you an array with the names of the constants, which are
> the names of the exception claesses you're interested in. The map method
> transforms the array of names in an  array of classes, obtained using
> Errno.const_get

Ugly, but I guess it will have to do.  I'll probably wrap that in its
own method.  Perhaps I can convince Nathaniel to either add a
"assert_raise_kind_of" method, or allow assert_raise to take another
argument.

> As for assert_raises being deprecated, I think it's simply a matter of names,
> since the method replacing it is simply assert_raise (without the final s).

Oh, I could have sworn they were both deprecated.  Perhaps I was
looking at old docs. Disregard.  I can't wait to go through all of my
tests and update those.  Not.

Thanks,

Dan