Here is my folder structure

/root
  /app
    __init__.py
    /main.py
  /tests
    test_something.py (from app.main import ...)

When I run pytest inside /root or /root/tests, I get the error message “cannot import module app”.

I change the folder structure to this and everything works fine.

/root
  /app
    __init__.py
    /main.py
  /tests
    __init__.py
    test_something.py (from app.main import ...)

I want to know how adding this init file revoles pytest import error.