Ticket #84 (assigned)

From Kevin Dangoor:

A coworker found an interesting bug in test generators. Apparently,
py.test does the same thing. Maybe this is architecturally difficult
to contend with. Here's the test:

#! /usr/bin/env python

def test_list_loop():
   def check_list_loop(ls, len_expected):
       print ls
       assert len(ls) == len_expected
   ls = list()
   for i in range(0, 6):
       ls.append(i)
       yield check_list_loop, ls, i + 1

It appears that each yielded test is not run immediately, but is
collected up and *then* run. In this particular case, that fails
because a mutable object is involved (and mutated as part of the test
running). Changing that last line to

       yield check_list_loop, ls[:], i + 1

makes it work, because you're dealing with copies of the list each time.