pytest-dev / pytest-dev/pytest

ModuleNotFoundError when pytest not in venv

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topic: collection type: enhancement
Dominant language
Python
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Description

If pytest is installed system-wide but not in a venv, pytest will run but not find the dependencies installed in the venv. It would be nice if pytest would trigger a descriptive error if the ENV var VIRTUAL_ENV is set but pytest is not running from inside this venv.

pytest 7.2.1 from Debian bookworm (12)

Reproduce:

  1. Ensure pytest is installed system-wide
  2. Create venv
  3. Activate venv and install any module (e.g. foo) not present in system (but not pytest)
  4. Create a test file importing this module
  5. Run pytest, it will produce "E ModuleNotFoundError: No module named 'foo'"

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Research direction

Reproduce the reported setup: install pytest system-wide, create and activate a virtual environment, install a module only there, and run a test that imports it. Start by tracing pytest's invocation and environment handling; done means this mismatch produces a descriptive error when VIRTUAL_ENV is set and pytest is outside that environment.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
testing-qa
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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