ModuleNotFoundError with pytest

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

Use $ python -m site, or this code fragment to debug such issues:

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

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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.

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.

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.)

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Good practice: use a Makefile or some other automation tool

If you 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: test
test:
    PYTHONPATH=. pytest

Which allows you to simply run:

make test

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