Why python -m pytest fails, but pytest works?

[moi15moi]

When I run python -m pytest in my project, I get a ModuleNotFoundError exception:

% python -m pytest
====================================================================== test session starts =======================================================================
platform darwin -- Python 3.12.11, pytest-8.4.1, pluggy-1.6.0
rootdir: /System/Volumes/Data/src/bugs/bug1989/Coverage-bug-report
configfile: pyproject.toml
collected 0 items / 1 error

============================================================================= ERRORS =============================================================================
__________________________________________________________ ERROR collecting tests/test_a_cpp_module.py ___________________________________________________________
ImportError while importing test module '/System/Volumes/Data/src/bugs/bug1989/Coverage-bug-report/tests/test_a_cpp_module.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/usr/local/pyenv/pyenv/versions/3.12.11/lib/python3.12/importlib/__init__.py:90: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
tests/test_a_cpp_module.py:1: in <module>
    from coverage_bug_report import add
coverage_bug_report/__init__.py:3: in <module>
    from .a_cpp_module import add
E   ModuleNotFoundError: No module named 'coverage_bug_report.a_cpp_module'
==================================================================== short test summary info =====================================================================
ERROR tests/test_a_cpp_module.py
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
======================================================================== 1 error in 0.05s ========================================================================

But, when I run pytest, the tests pass without any issue.

Is this a known problem when pytest tries to import pybind11 module? Is there a way to make it work properly?

I made a small project to show you the problem: https://github.com/moi15moi/Coverage-bug-report

The documentation don't really mention any possible fix.

PS: Note that when I install the project with pip install ., I have this issue. But, when I install the project with pip install --no-build-isolation --editable . (note that --no-build-isolation is needed because of this), I don't have it.

[paultiq]

Look at the sys.path difference when running pytest and python -m pytest. python -m pytest will add the current directory to your sys.path

Your test will fails when run with the cwd added your PATH, and passes without it.

You could also see this by cd'ing to another directory before running python -m pytest.

[paultiq]

This can be reproduced without pytest by running, from the root of your repo:

export PYTHONPATH=`cwd`
python tests/test_a_cpp_module.py

Traceback (most recent call last):
File "/home/.../Coverage-bug-report/tests/test_a_cpp_module.py", line 1, in
from coverage_bug_report import add
File "/home/.../Coverage-bug-report/coverage_bug_report/init.py", line 3, in
from .a_cpp_module import add
ModuleNotFoundError: No module named 'coverage_bug_report.a_cpp_module'

[moi15moi]

So, the problem may be from meson-python?