testing -- what to do for testing code with behaviour dependant upon which files exist?

[André Malo]

* Brian van den Broek wrote:

> The relevant part of the validation method code looks like:
> 
>      # self.universe_files is a list of file paths
>      non_existent_files = [ x for x in self.universe_files if
>                                         not os.path.isfile(x) ]
>      if non_existent_files:
>          raise Files_dont_existError, non_existent_files
> 
> I can test the custom error class just fine, but I don't see how to
> test the validation method itself.

The logic is simple -- you don't want to test os.path.isfile, so mock it.
Just encapsulate the os.path.isfile call in an own method, which can be
overridden by your test.

nd
-- 
# André Malo, <http://pub.perlig.de/> #