A context manager that enables go quickly in the future or in the past with datetime.datetime.now(). This may be useful in lots of unit tests.

mock_datetime_now.py

# -*- coding: utf-8 -*-
"""Mock datetime.datetime.now()"""

import contextlib
import datetime

@contextlib.contextmanager
def mock_datetime_now(*args, **kwargs):
    """Context manager for mocking out datetime.datetime.now() in unit tests.

    :param args: provide arguments as expected by :class:`datetime.datetime`
      http://docs.python.org/2.7/library/datetime.html#datetime.datetime

    Example::

      >>> with mock_datetime_now(2011, 2, 3, 10, 11):
      ...     now = datetime.datetime.now()
      >>> now == datetime.datetime(2011, 2, 3, 10, 11)
      True
    """
    class MockDateTime(datetime.datetime):
        @classmethod
        def now(cls):
            return cls(*args, **kwargs)

    real_datetime = datetime.datetime
    datetime.datetime = MockDateTime
    try:
        yield datetime.datetime
    finally:
        datetime.datetime = real_datetime


if __name__ == '__main__':
    import doctest
    doctest.testmod()