Way to implement CI test to check if function argument is valid?

Question

Let's say I have a python function and dictionary as follows:

d = {"a": 1, "b": 2, "c": 3}
def foo(input):
    return d[input]

Is there a way when I push my code to GitHub (presumably with some sort of continuous integration) to check that all calls of foo only use one of the keys of d as the input argument, and if there is a call with an invalid argument, to flag it or raise an alert?

For example:

foo("a") # no flag
foo("d") # flag/alert

I know how I would raise an exception or ValueError at runtime, but I'm looking for a CI solution to include in our GitHub workflow. Right now we are using Travis-CI for our custom tests and the standard CodeQL tests provided by LGTM. I looked into using custom CodeQL via LGTM, but I couldn't quite figure it out. I'd be fine implementing it in either of those continuous integrations or implementing a third.

Answer 1

we are in your wrkDir where your pythonFunction.py is, where your foo(input), d dict is inside. In that wrkDir create file tests.py:

import unittest

class TestPythonFunction(unittest.TestCase):
    # define here all required cases
    ALL_DICT_REQUIREMENTS_ =(
        ('a', 1), 
        ('b', 2), 
        ('c', 3)
    )

    
    def test_dictFoo(self):
        # pythonFunction reflects to your pythonFunction.py
        from pythonFunction import foo
        # test all required patterns
        for pattern in TestPythonFunction.ALL_DICT_REQUIREMENTS_:
            key = pattern[0]
            value = pattern[1]
            self.assertIs(foo(key), value)
        # test function is raising error if key doesn't exists
        with self.assertRaises((KeyError)):
            foo('nonsenseKey')
    

if __name__ == '__main__':
    unittest.main()
    

In wrkDir run

python tests.py

expexted output:

.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK

The tests.py exit code is 0 (all tests succeeded), or none 0 if some test failed, so you can control your CI task accordingly,

python tests.py && git push || echo "Bad, check tests for error"