[Python] Unit Test is not executable by using Pytest

I am currently using Pytest as my unit test framework in my Python project (which is a backend service based on AWS Chalice framework). I put my unit tests under a repository named tests as the document says, and it works well.

However, when I try to run a unit test in the same structure in a pure python project, it went failed by receiving ModuleNotFoundError: No module named 'src'.

My structure looks like,

.
├── src
│ └── module_a.py
└── tests
└── test_module_a.py


./src/module_a.py

def square(num: int) -> int:
"""Returns the square of a number."""
return num * num


./tests/test_module_a.py

from src.module_a import square

def test_square():
assert square(8) == 64


and the error I got is

Traceback:
../../../opt/anaconda3/envs/py3.11/lib/python3.11/importlib/__init__.py:126: in import_module
return _bootstrap._gcd_import(name[level:], package, level)
tests/test_module_a.py:1: in <module>
from src.module_a import square
E ModuleNotFoundError: No module named 'src'
=========================================================================== short test summary info ===========================================================================
ERROR tests/test_module_a.py


I have take a look into my previous project, and just can't find where the environment path is setup. I'm so confused and don't know how to figure it.

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