Python: know function is called from a unittest?

Question

Is there a way to know in Python if a function is called from the context of a unittest execution or a debugging run?

For the context, I am trying to unittest a code where I use functions that perform a database call. In order to avoid database calls during the test of that function (DB calls are tested separately), I am trying to make the DB IO functions aware of their environement and to mock when they are called within a unittest and log additional variables during a debug run.

My current aproach is to read/write environment variables, but it seems a little bit of an overkill and I think Python must have a better mechanism for that.

Edit: Here is the example of a function I am trying to unittest:

from Database_IO import Database_read

def some_function(significance_level, time_range)
    data = Database_read(time_range)
    significant_data = data > significance_level
    return significant_data

Can't you inject the mock in your object? You're sort of trying to do it backward, which might be a sign your code isn't designed correctly. — Vincent Savard
– Vincent Savard, Commented Nov 20, 2015 at 20:59
You should mock the database call within your tests / testing framework. This keeps your application code clean. — Simeon Visser
– Simeon Visser, Commented Nov 20, 2015 at 20:59
It might be worth it to show a small example of what you're trying to test. — Vincent Savard
– Vincent Savard, Commented Nov 20, 2015 at 21:20
mock.patch('mod.foo', ...) mocks the function foo imported from mod, regardless of how deeply inside the test code it appears. — chepner
– chepner, Commented Nov 20, 2015 at 21:32
Instead of importing it with import foo, just mock the entire module: foo = mock.Mock(). You may need a significant amount of configuration of the resulting Mock instance in order for your test code to work. — chepner
– chepner, Commented Nov 21, 2015 at 0:26

chepner · Accepted Answer · 2015-11-21 00:30:52Z

6

In my opinion, if you write your function to behave in a different way when tested, you are not really testing it.

To test the function I'd mock.patch() the database object, and then check it has used correctly in your function.

The most difficult thing when you start using the mock library is to find the correct object to replace.

In your example, if in your_module you import the Database_read object from the Database_IO module, you can test it by using a code similar to the following

with mock.patch('your_module.Database_read') as dbread_mock:
    # prepare the dbread_mock
    dbread_mock.return_value = 10
    # execute a test call
    retval = some_function(3, 'some range')
    # check the result
    dbread_mock.assert_called_with('some range')

edited Nov 21, 2015 at 0:30

chepner

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answered Nov 20, 2015 at 22:31

mnencia

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