Clever Geek Handbook

How to write Python time sensitive tests

Suppose I have function

:

def third_day_from_now():
    return datetime.date.today() + datetime.timedelta(days=3)

I want to write tests for this function? I know that if today 25th

, the function should return 28

. Is there a way to somehow make the object datetime

return current date

like 25

?

+3


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3 answers


freezegun

makes mocking datetime very easy.



from freezegun import freeze_time

@freeze_time("2015-02-25")
def test_third_day_from_now():
    assert third_day_from_now() == datetime.datetime(2015, 2, 28)
+3


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Update function to get the input date as an argument (default to None)

Then test the function by calling with the ie Custom Date argument and no argument.



Demo

>>> def third_day_from_now(input_date=None):
...      if input_date:
...           return input_date + datetime.timedelta(days=3)
...      else:
...           return datetime.date.today() + datetime.timedelta(days=3)
... 

>>> print "Today + 3:", third_day_from_now()
Today + 3: 2015-07-12

>>> input_date = datetime.datetime.strptime('25-05-2015', "%d-%m-%Y").date()
>>> print "Custom Date:", input_date
Custom Date: 2015-05-25
>>> print "Custom Date + 3:", third_day_from_now(input_date)
Custom Date + 3: 2015-05-28
+1


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No, you won't try to change the system clock, rather, you can change the function to something you can check:

def third_day_from(someday):
    """Returns the day three days after someday
    :param someday: a datetime to start counting from
    """
    return someday + datetime.timedelta(days=3)

def test_third_day(...)
    today = datetime(25, 5, 2005)
    thirdday = datetime(28, 5, 2005)
    self.assertEqual(third_day_from(today), thirdday)
0


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