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anybox.testing.datetime /

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anybox
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A module to allow playing with time in tests.

This README is also a doctest. To it and other doctests for this package, simply do:

nosetests --with-doctest --doctest-extension=txt

Before anything, the package must be imported in order to replace the regular datetime module with the modified one:

>>> import anybox.testing.datetime
>>> from datetime import datetime
>>> import time

Let's keep the real value of now around:

>>> start = datetime.now()
>>> start_t = time.time()

Then you can:

>>> datetime.set_now(datetime(2001, 01, 01, 3, 57, 0))
>>> datetime.now()
datetime(2001, 1, 1, 3, 57)
>>> datetime.today()
datetime(2001, 1, 1, 3, 57)

The time module goes along:

>>> datetime.fromtimestamp(time.time())
datetime(2001, 1, 1, 3, 57)

Note that you can expect a few microseconds difference (not displayed here because datetime.fromtimestamp ignores them).

Don't forget afterwards get back to the regular system clock, otherwise many pieces of code might get very suprised if the system clock looks as if it's frozen:

>>> datetime.real_now()

Now let's check it worked:

>>> now = datetime.now()
>>> now > start
True
>>> from datetime import timedelta
>>> now - start < timedelta(0, 0, 10000) # 10 ms
True

And with the time module:

>>> now_t = time.time()
>>> now_t > start_t
True
>>> now_t - start_t < 0.01 # 10 ms again
True

Other constructors are still available (this is a non regression test):

>>> import datetime
>>> datetime.time(3, 57, 0)
datetime.time(3, 57)
>>> datetime.datetime(2013, 1, 1, 3, 57, 0)
datetime(2013, 1, 1, 3, 57)
>>> datetime.date(2013, 1, 1)
datetime.date(2013, 1, 1)

Our replacement class is the one loaded from the datetime module, but instances of the original datetime class behave exactly as instances of our datetime.datetime. This is needed because most computational methods, actually return an object of the original datetime class. This works with python >= 2.6 only.

First let's check that our class is a subclass of the original one. If this fails, this test does not mean anything anymore:

>>> datetime.datetime is datetime.original_datetime
False
>>> issubclass(datetime.datetime, datetime.original_datetime)
True

Then let's demonstrate the behaviour:

>>> odt = datetime.original_datetime(2012, 1, 1)
>>> isinstance(odt, datetime.datetime)
True
>>> issubclass(datetime.original_datetime, datetime.datetime)
True

We'll need a tzinfo subclass from now on.

>>> from datetime import tzinfo
>>> class mytzinfo(tzinfo):
...     def utcoffset(self, dt):
...         return timedelta(hours=2)
...     def dst(self, dt):
...         return timedelta(0)

When anybox.testing.datetime is not in use, the optional time zone argument of now can be passed without error

>>> n = datetime.datetime.now(mytzinfo())