FunAlone

A small python library that makes it easy to test a function alone, that is, mocking all dependencies. True unittests, without having to manually look and add every called function to an increasing list of @mock.patch decorators.

Example

Say you have a function named do_a_lot_of_stuff and you want to test it with unittest, only testing the functions code, not the function that it calls within.

def do_a_lot_of_stuff(arg: int):
    if arg > 5:
        result = do_this(arg)
    elif arg < 0:
        result = do_that(arg)
    else:
        result = do_nothing(arg)
    
    return result

In this case you might want to know which external function has been called, depending on the input, without having the code actually call that function (which could have side effects and should have it's own unit tests).

class Test(unittest.TestCase):
    def test_do_a_lot_of_stuff_with_5(self):
        with IsolatedFunctionClone(
            do_a_lot_of_stuff
            ) as do_a_lot_of_stuff_clone:

            # This calls a function clone with an isolated context.
            # All external names are mocked.
            do_a_lot_of_stuff_clone(5)

            # You can access this context later to assert calls,
            # And you can use the original functions to do this,
            # so it's all refactor-friendly.
            do_a_lot_of_stuff_clone.context[do_this].assert_not_called()
            do_a_lot_of_stuff_clone.context[do_that].assert_not_called()
            do_a_lot_of_stuff_clone.context[do_nothing].assert_called_once()

There are more parameters and ways to use the library, this is only a basic example.

Installation

You can install the latest version with pip:

pip install funalone

Tests

There is a small collection of unittests in the test folder. You can run them using unittest.

Credits

This project is developed by Borja Martinena (borjamartinena[at]gmail.com).