Testing properties that are date-related

Fri Oct 7 07:46:46 EDT 2011

Are there best practices for testing dates that are properties 
which take the current date into consideration? I have something 
like
 class Foo:
 def _get_year_range(self):
 return (self._min_year, self._max_year)
 def _set_year_range(self, year):
 if isinstance(year, tuple):
 _min, _max = map(window_date, year)
 if _min > _max: _min, _max = _max, _min
 else: # a raw int
 _min = _max = window_date(year)
 self._min_year, self._max_year = _min, _max
 year_range = property(
 fget=_get_year_range,
 fget=_get_year_range,
 )
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:
 class TestFoo:
 def test_year_range(self):
 around = date(2011,1,1)
 f = Foo()
 f.year_range = (97, 84)
 self.assertEqual(f.year_range, (1984, 1997))
Any suggestions/tips/hints? Thanks,
-tkc