How to test my script in a github repo which is dependent upon other files in the repo

In my github repository, I have a python script say script.py. I want to check if this produces the desired output or not?
I can copy the code of this file ad run it on my local machine but this script.py is using functions and modules from other files in the repository as well. So I cannot simply copy script.py and run it to test it.

So what should I do? How do I make sure that this produces the right output?

I am very new to git and VC so please answer elaborately.