Testing properties that are date-related

[Tim Chase]

On 10/07/11 07:38, Peter Otten wrote:
>> Are there best practices for testing dates that are properties
>> which take the current date into consideration
>>
>> The problem is that the behavior of the window_date function
>> depends on the current date (the function makes a guess about
>> adding the century if the year was<100).  It *does* take an
>> "around" parameter that defaults to the current date.  So for
>> pure testing of the window_date() function, I can hard-code some
>> date where I know what the expected values should be.
>>
>> However if I want to write a test-harness for my property, I have
>> no way (AFAIK) to pass in this fixed date to _set_year_range() so
>> that the success/failure of my tests doesn't depend on the day I
>> run them
>
> Temporarily replace the window_date() function with something that you can
> control completely. Assuming Foo and window_date are defined in foo.py:
>
> # untested
> import foo
>
> class TestFoo:
>      def setUp(self):
>          foo.window_date = functools.partial(foo.window_date,
> around=date(2011, 1, 1))
>      def tearDown(self):
>          foo.window_date = foo.window_date.func
>      def test_year_range(self):
>          f = Foo()
>          f.year_range = (97, 84)
>          self.assertEqual(f.year_range, (1984, 1997))

I had to twiddle my class code a bit to make sure it referenced 
module.window_date() everywhere instead of just a raw 
window_date() (originally pulled in via "from module import 
window_date") so that it picked up the new function, but 
otherwise it worked like a charm.

(there was also the matter of some function properties that were 
used for an undetailed parameter to allow for suggesting that the 
window_date bias backwards, forwards or around the current date, 
but a little hackery took care of that too, just copying the 
germane properties from the saved function object to the result 
of the partial() call)

Thanks!

-tkc