How to configure pyproject.toml for a pip package to enable one Python script to execute another via command line?

Question

I would like to create a pip package where one python script can execute the other script over the command line.

Take this as an example:

my-package/
└── my-package
    ├── script.py
    └── tests.py

with script.py:

import pytest

def run():

    # run the other script
    pytest.main(["tests.py"])
    
    # then do the actual stuff
    print("I did something!")

and tests.py:

import pytest

class Test:
    
    def test_stuff(self):
        if not 1 == 2:
            pytest.fail('1 does not equal 2')

How can I configure my pyproject.toml file so that the run() function inside script.py always "knows" where to find tests.py so it can execute it via pytest.main()? Right now, I have the problem that the run() function expects tests.py to be always in the directory that I am currently in. Of course that's not the case. I need a way to tell the run function that it will find tests.py in the same directory where itself is located.

Note: I saw a few suggestions but they always refer to specific functions inside scripts that are made available as command-line options. But in my case one script should call the whole other script not just one single function inside of it.

Possibly related:

how to run a script using pyproject.toml settings and poetry?