FreezeGun: Let your Python tests travel through time

FreezeGun is a library that allows your python tests to travel through time by mocking the datetime module.

Usage

Once the decorator or context manager have been invoked, all calls to datetime.datetime.now(), datetime.datetime.utcnow(), and datetime.date.today() will return the time that has been frozen.

Decorator

from freezegun import freeze_time

@freeze_time("2012-01-14")
def test():
    assert datetime.datetime.now() == datetime.datetime(2012, 01, 14)

# Or class based

@freeze_time("2012-01-14")
class Tester(object):
    def test_the_class(self):
        assert datetime.datetime.now() == datetime.datetime(2012, 01, 14)

Context Manager

from freezegun import freeze_time

def test():
    assert datetime.datetime.now() != datetime.datetime(2012, 01, 14)
    with freeze_time("2012-01-14"):
        assert datetime.datetime.now() == datetime.datetime(2012, 01, 14)
    assert datetime.datetime.now() != datetime.datetime(2012, 01, 14)

Raw use

from freezegun import freeze_time

freezer = freeze_time("2012-01-14 12:00:01")
freezer.start()
assert datetime.datetime.now() == datetime.datetime(2012, 01, 14, 12, 00, 01)
freezer.stop()

Timezones

from freezegun import freeze_time

@freeze_time("2012-01-14 03:21:34", tz_offset=-4)
def test():
    assert datetime.datetime.utcnow() == datetime.datetime(2012, 01, 14, 03, 21, 34)
    assert datetime.datetime.now() == datetime.datetime(2012, 01, 13, 23, 21, 34)

    # datetime.date.today() uses local time
    assert datetime.date.today() == datetime.datetime(2012, 01, 13)

Nice inputs

FreezeGun uses dateutil behind the scenes so you can have nice-looking datetimes

@freeze_time("Jan 14th, 2012")
def test_nice_datetime():
    assert datetime.datetime.now() == datetime.datetime(2012, 01, 14)

Warning

For the time being, if you use datetime as from datetime import datetime; now = datetime.now() then freezegun module must be imported before the datetime module is ever imported for this to work. If you use datetime as import datetime; now = datetime.datetime.now(), then you're good to go without worrying about import order.

Installation

To install FreezeGun, simply:

$ pip install freezegun

mlakewood/freezegun