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Let your Python tests travel through time

Project description

FreezeGun: Let your Python tests travel through time
====================================================


.. image:: https://secure.travis-ci.org/spulec/freezegun.png?branch=master
:target: https://travis-ci.org/spulec/freezegun
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:target: https://coveralls.io/r/spulec/freezegun

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(), datetime.date.today(), time.time(), time.localtime(), time.gmtime(), and time.strftime() will return the time that has been frozen.

Decorator
~~~~~~~~~

.. code-block:: python

from freezegun import freeze_time
import datetime
import unittest


@freeze_time("2012-01-14")
def test():
assert datetime.datetime.now() == datetime.datetime(2012, 1, 14)

# Or a unittest TestCase - freezes for every test, from the start of setUpClass to the end of tearDownClass

@freeze_time("1955-11-12")
class MyTests(unittest.TestCase):
def test_the_class(self):
assert datetime.datetime.now() == datetime.datetime(1955, 11, 12)

# Or any other class - freezes around each callable (may not work in every case)

@freeze_time("2012-01-14")
class Tester(object):
def test_the_class(self):
assert datetime.datetime.now() == datetime.datetime(2012, 1, 14)

Context Manager
~~~~~~~~~~~~~~~

.. code-block:: python

from freezegun import freeze_time

def test():
assert datetime.datetime.now() != datetime.datetime(2012, 1, 14)
with freeze_time("2012-01-14"):
assert datetime.datetime.now() == datetime.datetime(2012, 1, 14)
assert datetime.datetime.now() != datetime.datetime(2012, 1, 14)

Raw use
~~~~~~~

.. code-block:: python

from freezegun import freeze_time

freezer = freeze_time("2012-01-14 12:00:01")
freezer.start()
assert datetime.datetime.now() == datetime.datetime(2012, 1, 14, 12, 0, 1)
freezer.stop()

Timezones
~~~~~~~~~

.. code-block:: python

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, 1, 14, 3, 21, 34)
assert datetime.datetime.now() == datetime.datetime(2012, 1, 13, 23, 21, 34)

# datetime.date.today() uses local time
assert datetime.date.today() == datetime.date(2012, 1, 13)

Nice inputs
~~~~~~~~~~~

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

.. code-block:: python

@freeze_time("Jan 14th, 2012")
def test_nice_datetime():
assert datetime.datetime.now() == datetime.datetime(2012, 1, 14)

`tick` argument
~~~~~~~~~~~

FreezeGun has an additional `tick` argument which will restart time at the given
value, but then time will keep ticking. This is alternative to the default
parameters which will keep time stopped.

.. code-block:: python

@freeze_time("Jan 14th, 2020", tick=True)
def test_nice_datetime():
assert datetime.datetime.now() > datetime.datetime(2020, 1, 14)

Manual ticks
~~~~~~~~~~~~

Freezegun allows for the time to be manually forwarded as well

.. code-block:: python

def test_manual_increment():
initial_datetime = datetime.datetime(year=1, month=7, day=12,
hour=15, minute=6, second=3)
with freeze_time(initial_datetime) as frozen_datetime:
assert frozen_datetime() == initial_datetime

frozen_datetime.tick()
initial_datetime += datetime.timedelta(seconds=1)
assert frozen_datetime() == initial_datetime

frozen_datetime.tick(delta=datetime.timedelta(seconds=10))
initial_datetime += datetime.timedelta(seconds=10)
assert frozen_datetime() == initial_datetime

Moving time to specify datetime
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Freezegun allows moving time to specific dates

.. code-block:: python

def test_move_to():
initial_datetime = datetime.datetime(year=1, month=7, day=12,
hour=15, minute=6, second=3)

other_datetime = datetime.datetime(year=2, month=8, day=13,
hour=14, minute=5, second=0)
with freeze_time(initial_datetime) as frozen_datetime:
assert frozen_datetime() == initial_datetime

frozen_datetime.move_to(other_datetime)
assert frozen_datetime() == other_datetime

frozen_datetime.move_to(initial_datetime)
assert frozen_datetime() == initial_datetime

Parameter for ``move_to`` can be any valid ``freeze_time`` date (string, date, datetime).


Default Arguments
~~~~~~~~~~~~~~~~~

Note that Freezegun will not modify default arguments. The following code will
print the current date. See `here <http://docs.python-guide.org/en/latest/writing/gotchas/#mutable-default-arguments>`_ for why.

.. code-block:: python

from freezegun import freeze_time
import datetime as dt

def test(default=dt.date.today()):
print(default)

with freeze_time('2000-1-1'):
test()


Installation
------------

To install FreezeGun, simply:

.. code-block:: bash

$ pip install freezegun

On Debian (Testing and Unstable) systems:

.. code-block:: bash

$ sudo apt-get install python-freezegun

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