ModuleNotFoundError with pytest

Question

I want my tests folder separate to my application code. My project structure is like so

myproject/
  myproject/
    myproject.py
    moduleone.py
  tests/
    my         


        

Answer 1

Kept everything same and just added a blank test file at the root folder .. Solved

Here are the findings, this problem really bugged me for a while. My folder structure was

mathapp/
    - server.py  
    - configuration.py 
    - __init__.py 
    - static/ 
       - home.html  
tests/            
    - functional 
       - test_errors.py 
    - unit  
       - test_add.py

and pytest would complain with the ModuleNotFoundError.

I introduced a mock test file at the same level as mathsapp and tests directory. The file contained nothing. Now pytest does not complain.

Result without the file

$ pytest
============================= test session starts =============================
platform win32 -- Python 3.8.2, pytest-5.4.2, py-1.8.1, pluggy-0.13.1
rootdir: C:\mak2006\workspace\0github\python-rest-app-cont
collected 1 item / 1 error

=================================== ERRORS ====================================
_______________ ERROR collecting tests/functional/test_func.py ________________
ImportError while importing test module 'C:\mainak\workspace\0github\python-rest-app-cont\tests\functional\test_func.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
tests\functional\test_func.py:4: in <module>
    from mathapp.service import sum
E   ModuleNotFoundError: No module named 'mathapp'
=========================== short test summary info ===========================
ERROR tests/functional/test_func.py
!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!
============================== 1 error in 0.24s ===============================

Results with the file

$ pytest
============================= test session starts =============================
platform win32 -- Python 3.8.2, pytest-5.4.2, py-1.8.1, pluggy-0.13.1
rootdir: C:\mak2006\workspace\0github\python-rest-app-cont
collected 2 items

tests\functional\test_func.py .                                          [ 50%]
tests\unit\test_unit.py .                                                [100%]

============================== 2 passed in 0.11s ==============================

Answer 2

So it seems that the sys.path has to include the application directory rather than the project root folder containing the application directory and test directory.

So in my case /my/local/path/myproject/myproject/ had to be in sys.path rather than /my/local/path/myproject/.

Then I could run pytest in /my/local/path/myproject/ (didn't need python -m pytest). This meant that the modules within /myproject/myproject/ could find each other and the tests as well without any namespace nesting.

So my tests looked like

 from moduleone import ModuleOne
 import pytest

 def test_fun():
     assert ModuleOne.example_func() == True

That said, there seem to be many gotchas, so I have no idea if this is correct..

Answer 3

Solution: use the PYTHONPATH env. var

PYTHONPATH=. pytest

As mentioned by @J_H, you need to explicitly add the root directory of your project, since pytest only adds to sys.path directories where test files are (which is why @Mak2006's answer worked.)

---

Good practice: use a Makefile or some other automation tool

If you are lazy and do not want to type that long command all the time, one option is to create a Makefile in your project's root dir with, e.g., the following:

.PHONY: install test

default: test

install:
    pip install --upgrade .

test:
    PYTHONPATH=. pytest

Which allows you to simply run:

make test

or (even shorter)

make

Another common alternative is to use some standard testing tool, such as tox.

Answer 4

Not sure if this solution was specific to my problem, but I simply add __init__.py to my tests folder and that solved the problem.

Answer 5

I ran into this issue as well and am using poetry for dependency management and direnv for my project specific environment variables. Please note, I am relatively new to Python so I don't know if this is the correct fix.

Here is my entire .envrc file:

layout_poetry() {
  if [[ ! -f pyproject.toml ]]; then
    log_error 'No pyproject.toml found.  Use `poetry new` or `poetry init` to create one first.'
    exit 2
  fi

  local VENV=$(poetry env list --full-path | cut -d' ' -f1)
  if [[ -z $VENV || ! -d $VENV/bin ]]; then
    log_error 'No created poetry virtual environment found.  Use `poetry install` to create one first.'
    exit 2
  fi
  VENV=$VENV/bin
  export VIRTUAL_ENV=$(echo "$VENV" | rev | cut -d'/' -f2- | rev)
  export POETRY_ACTIVE=1
  PATH_add "$VENV"
}

layout poetry
export PYTHONDONTWRITEBYTECODE=1
export PYTHONPATH="$PWD/project_name"

I don't know if I need to layout poetry because it is supposed to be creating virtual environments for us already but this is what I coworker recommended so I went with it. Layout poetry also didn't work without that function and it didn't like when I added it to my zshenv so I added it here.

For this specific question, the last line is the money maker.

Answer 6

Be sure to include . dot in the $PYTHONPATH env var.

You can use this code fragment to debug such issues:

import pprint
import sys
pprint.pprint(sys.path)

Your question managed to use myproject at three different levels. At least during debugging you might want to use three distinct names, to reduce possible confusion.