holger krekel wrote: > Hi Philippe, Neil, > > On Fri, Apr 24, 2009 at 14:45 +0200, Philippe Fremy wrote: >> Neil Shepperd wrote: >>> Hi, >>> >>>> I have found that storing the results of the call I want to test the >>>> result of, and then asserting the result generally eliminates these >>>> errors. >>>> >>>> For example: >>>> >>>> assert Foo() == 23 >>>> >>>> often caused me problems with that message, however: >>>> >>>> foo = Foo() >>>> assert foo == 23 >>>> >>>> would not. >>>> >>>> I am not sure why that is the case but I was able to resolve the issue >>>> using the second form. >>> If I understand it correctly, the test handling magic evaluates each >>> part of the expression again, to display it in the fail traceback. >>> For example, in the traceback of some test it will say: >>> >>> def test_xxx(): >>> E assert Foo() == 23 >>>> assert 0 == 23 >>> If Foo() returns 0. It is run again get the value 0 to substitute into >>> the error message. However if the second time it is run Foo() actually >>> works correctly and returns 23, this value is obviously not correct, >>> because if it were the assert would have passed. >>> >>> I suspect maybe py.test is evaluating t.isAlive() again to substitute >>> into the if-expression, resulting in confusion when the result changes >>> to True. If that is the case, you might have to do something like >>> >>> checker.stop( False ) >>> is_alive = t.isAlive() >>> is_finished = checker.isFinished() >>> if not is_alive: assert False >>> if is_finished: assert False >>> >>> >>> Hope this made sense, >> Thanks, it makes sense now on the cause of the error. This ought to be >> documented somewhere in py.test > > i agree, the error message is slightly mysterious. what about this: > > def test_inconsistent(): > def f(l=[1,0]): > return l.pop() >> assert f() > E AssertionError: (assert failed but re-evaluating the > assert expression for printing intermediate values lead to a > True value. advise: avoid side-effects in assert expressions > or use --nomagic)
I like it :-) As long as it's documented somewhere what's the cause and how to get around it, I'm fine. cheers, Philippe _______________________________________________ py-dev mailing list py-dev@codespeak.net http://codespeak.net/mailman/listinfo/py-dev
