Hello,
I have a couple questions regarding the best way to do date math in
SQLAlchemy with Postgresql and how I can write fixture-based unit
tests for this without requiring an actual database in my test.
There's 2 specific types of dates which I need to be retrieving.
Written in SQL these would be:
1) CURRENT_TIMESTAMP
2) CURRENT_TIMESTAMP + interval 'X months'
I know that I can use sqlalchemy.func.current_timestamp() to retrieve
the first, but this breaks when I try to unit test it and there is no
database session present. For example, consider the following code:
@property
def is_active(self):
return ((not self.date_closed) or
(self.date_closed >= sa.func.current_timestamp()))
If I unit test this with several mock fixtures and there's no database
present, is_active fails when it encounters a fixture with a
"date_closed":
AssertionError: True is not False
AssertionError: <sqlalchemy.sql.expression._BinaryExpression object at
0x2a684d0> is not False
I would like to be able to use our postgresql database to retrieve the
current_timestamp as well as "CURRENT_TIMESTAMP + interval 'X months'"
and preserve the ability to unit test this code without requiring an
actual database. One idea my boss suggested was to use the Fudge
module in my tests to overload sqlalchemy.func.current_timestamp()
with a function that uses python's datetime module to return the
current timestamp. Thus, when run in production, my code will use the
database to get the current time, but when run in a unit test, we
avoid a broken test by instead using python's datetime to get the
current timestamp.
Does anyone have any experience or examples of this type of approach?
Also, while this seems like it will work for getting the current time,
how would I use the same approach to get "CURRENT_TIMESTAMP + interval
'X months'"? I don't see a pre-written
"sqlalchemy.func.current_timestamp_plus_interval('X months')
function. Do I need to write my own? If so, am I best off using raw
SQL or is there some other mechanism to do date math in SQLAlchemy?
Thanks for any help/guidance you can give me.
-Dan
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