pytest parametrize the array tests in `test_functions.py`

[Michael-J-Ward]

Describe the solution you'd like
Each UDF in src/functions.py should have its own test case in test_functions.py instead of testeing a bunch of functions in a single test case.

TODO

• pytest.mark.parameterize the functions
• ensure that every function in src/functions.rs has a test case

[raulcd]

Is this supposed to be closed due to #678 being merged?

[Michael-J-Ward]

Gracias. Closing.