2.0 KiB
Python tests run with mutator's virtualenv
Mutator runs a Python project's tests with mutator's own interpreter. That interpreter does not have the project installed, so the baseline fails and no mutants run.
What happened
From /Users/unclebob/projects/crapper:
/Users/unclebob/projects/mutator/mutator --use-existing-coverage
Every file that still had mutants to run failed the baseline:
Baseline failed for src/crapper/cli.py: /Users/unclebob/projects/mutator/.venv/bin/python -m pytest
E ModuleNotFoundError: No module named 'crapper'
Mutator exited 2. The same suite passes under crapper's virtualenv. ./crapper collected 120 tests and they passed.
This command gets past the baseline, because it names crapper's interpreter:
/Users/unclebob/projects/mutator/mutator --use-existing-coverage \
--test-command "/Users/unclebob/projects/crapper/.venv/bin/python -m pytest"
Cause
./mutator starts mutator/.venv/bin/python. _python_command in src/mutator/runner.py builds the test command from that process:
return f"{sys.executable} -m pytest"
sys.executable is mutator's Python. Crapper is not installed in mutator/.venv.
Mutator can still import crapper inside its own process. ensure_crapper() in src/mutator/crapper_link.py inserts ../crapper/src onto sys.path. Pytest is a new process and does not see that insertion.
The baseline also runs in the real tree, before any worker exists. _prefer_worker_sources adds PYTHONPATH only when the working directory is inside target/mutation-workers, so the baseline has no path to the project sources either.
Fix
When the project under test has .venv/bin/python or venv/bin/python, use that interpreter in the test command. The path has to be absolute. Workers do not link .venv (SKIP_LINK in src/mutator/workers.py), so a relative .venv/bin/python is missing inside a worker.
If the project has no virtualenv, keep using mutator's Python.