Why does pytest return a ModuleNotFoundError when trying to import the src folder?

I have a project named unit_testing with 2 subfolders named src/ and tests/. In src there is a file called my_functions.py and in tests I have a file called test_my_functions.py.

This is the code in my_functions.py

def adding_pos(a, b, c):
if a < 0 or b < 0 or c < 0:
    output = f'function needs positive numbers'
else:
    output = a + b + c
return output

This is the code in test_my_functions.py

# import libs

import pytest
from src.my_functions import adding_pos


# %% test

class TestAddingPos(object):
    def test_adding(self):
        assert adding_pos(2, 5, 6) == 13

    def test_adding_neg(self):
        assert adding_pos(-1, 2, 3) == 'function needs positive numbers'

In the CLI, if I go to the test folder and then run pytest, I keep getting a ModuleNotfoundError saying the src module can not be found. I don’ understand why because in test_my_functions.py I import functions from src.my_functions and this works.

Why does this not work?

>Solution :

It looks like you’re trying to run tests in the tests/ directory that imports modules from the src/ directory. When you run pytest from the tests/ directory, it doesn’t know where to find the src/ directory.

To fix this, you can add an empty file called __init__.py to the src/ directory. This will make Python treat the directory as a package and allow you to import modules from it.

You can also add the path to the src/ directory to your system’s Python path. You can do this by adding the following code at the top of your test file:

import sys
sys.path.insert(0, '/path/to/src')

Replace /path/to/src with the actual path to your src/ directory.

Here’s the modified code with the path added to the system’s Python path:

import sys
sys.path.insert(0, '/path/to/src')

# import libs

import pytest
from src.my_functions import adding_pos


# %% test

class TestAddingPos(object):
    def test_adding(self):
        assert adding_pos(2, 5, 6) == 13

    def test_adding_neg(self):
        assert adding_pos(-1, 2, 3) == 'function needs positive numbers'

Replace /path/to/src with the actual path to your src/ directory.
I hope it works mate 🙂