DirExists and Not matchers produce poor feedback

[thomir]

I have a test that includes the following line:

self.expectThat(working_dir, Not(DirExists()))

When this assertion fails, the feedback I get isn't very readable:

'/tmp/tmpBNe_N9' matches MatchesAll(MatchesPredicate(<function exists at 0x7f0835277578>, '%s does not exist.'), MatchesPredicate(<function isdir at 0x7f0835277668>, '%s is not a directory.'))

This can be reproduced with the following:

>>> import os
>>> os.mkdir('/tmp/hello-testtools')
>>> from testtools.matchers import Not, DirExists
>>> matcher = Not(DirExists())
>>> mismatch = matcher.match('/tmp/hello-testtools')
>>> print(mismatch.describe())
'/tmp/hello-testtools' matches MatchesAll(MatchesPredicate(<function exists at 0x7f0835277578>, '%s does not exist.'), MatchesPredicate(<function isdir at 0x7f0835277668>, '%s is not a directory.'))

This is because DirExists is simply a function that returns an instance of MatchesAll:

def DirExists():
    """Matches if the path exists and is a directory."""
    return MatchesAll(
        PathExists(),
        MatchesPredicate(os.path.isdir, "%s is not a directory."),
        first_only=True)

and does not customize the __str__ method, which means we get the default MatchesAll str representation.

Being able to create new matcher types with a simple function is 'A Good Thing' (tm), but I wonder if we need a way to customise the __str__ representations of these new matchers.

Thoughts?

[rbtcollins]

Sure, being able to curry up something more useful would be great.