[TIP] Problem mocking a decorator

[Yoni Tsafir]

Hi guys,
I'm pretty new to the world of testing in python, and there's a problem I
ran into while trying to mock a decorator in the code I'm testing.
Tell me what am I doing wrong or if this is a missing feature in the mock
library.

I have the following code:

a.py:
-------
import sys

class BadArgsError(Exception):
    pass


def catch_bad_args(func):
    def call(*args, **kwargs):
        try:
            return func(*args, **kwargs)
        except BadArgsError, e:
            print >> sys.stderr, e.args[0]
            print
            sys.exit(1)

    call.__name__ = func.__name__
    call.__dict__ = func.__dict__
    call.__doc__  = func.__doc__
    return call

b.py
------
from a import BadArgsError, catch_bad_args

@catch_bad_args
def foo(arg):
    if arg > 2:
        raise BadArgsError("arg is bigger than 2")

    print "arg is ok"

test_b.py
-------------
import unittest
from b import foo
from a import BadArgsError
from mock import patch

def do_nothing_decorator(func):
    return func


class BTest(unittest.TestCase):
        @patch("a.catch_bad_args", do_nothing_decorator)
        def test_three_raises(self):
                self.assertRaises(BadArgsError, foo, 3)


Now running the tests:
-------------------------------
# python test_b.py
arg is bigger than 2

E
======================================================================
ERROR: test_three_raises (__main__.BTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_b.py", line 13, in test_three_raises
    self.assertRaises(BadArgsError, foo, 3)
  File "/usr/lib/python2.6/unittest.py", line 336, in failUnlessRaises
    callableObj(*args, **kwargs)
  File "/tmp/a.py", line 14, in call
    sys.exit(1)
SystemExit: 1

----------------------------------------------------------------------
Ran 1 test in 0.014s

FAILED (errors=1)


What am I doing wrong? I tried to change the patch to "b.catch_bad_args" and
I get the same results, I also tried @patch.object and other combinations...
No help


Thanks a lot!
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.idyll.org/pipermail/testing-in-python/attachments/20101228/8f057a25/attachment.html>