PyCharm/Testing/How To/Run All Pytest Tests in One Directory inside a Python Monorepo

• How To Run All Pytest Tests in One Directory inside a Python Monorepo with PyCharm

  • Goal

    • Run and debug only the tests in a chosen sub-directory of a large monorepo, regardless of how many other packages (and their tests) exist.

  • Preconditions

    • PyCharm 2023.3 or newer (Community or Professional)
    • Monorepo already opened as the project root in PyCharm
    • A working Python Py/Virtualenv interpreter (virtualenv, Poetry, or Conda) set for the project
    • pytest installed in that interpreter
    • Directory structure like:

      • monorepo/
        ├─ apps/
        │  └─ app_a/
        │     └─ tests/      ← focus_dir
        ├─ libs/
        │  └─ lib_x/
        │     └─ tests/
        └─ pyproject.toml    (or setup.cfg / requirements.txt)

  • Procedure

    • 1. Mark Source Roots with PyCharm/Tool/Project/Right Click/Mark Directory As/Sources Root

      • In the Project tool-window, right-click every top-level package (e.g. apps/app_a, libs/lib_x) → Mark Directory As ▶ Sources Root.
      • PyCharm then adds those folders to PYTHONPATH so imports inside tests resolve correctly.

    • 2. Tell PyCharm to Use pytest with PyCharm/Settings/Tools/Python Integrated Tools/Testing

      1. Settings ▶ Tools ▶ Python Integrated Tools

      2. Testing → Default test-runner pytest.

      3. Apply/OK.

    • 3. Create a PyCharm/Run Configuration for the Directory

      1. Top-right toolbar → Add Configuration…

      2. + → Python tests ▶ pytest.

      3. Name: tests-app_a.

      4. Target → choose Folder and select apps/app_a/tests.

      5. Working directory → set to the monorepo root (crucial so relative imports & pytest.ini are found).

      6. (Optional) Additional args:

      • -vv -s for verbose output
      • --maxfail=1 to stop after first failure

        1. Pick the same interpreter used by the project.

        2. Apply → Run 🟢.

    • 4. (Optional) Save as a Template

      • Back in Run/Debug Configurations, right-click the new entry → Save Configuration as Template.
      • Now you can duplicate it for other directories in seconds.

    • 5. Verify Discovery

      • After running once, the Run tool-window’s Test Tree should list only tests from apps/app_a/tests.
      • Green ▶ / Red ⨯ icons reflect pytest results; double-click any node to jump to code.

  • Troubleshooting

    • ImportError: module not found
      • Check that every package’s root is marked as Sources Root (step 1) and that your run config’s Working directory is the repo root.
    • “No tests were found”
      • Pytest’s discovery rules need files named test_*.py or *_test.py. Confirm naming; if you use a custom pattern, add -k "pattern" in Additional args.
    • Tests from other packages still run
      • Make sure the run config’s Target is Folder, not Script path or Parametrized tests.
      • Remove any --rootdir override in Additional args that might expand discovery.
    • Multiple virtualenvs
      • Each run config can point to a different interpreter. Pick the venv that has the dependencies for the target package.

  • References

    • PyCharm Docs — Run pytest tests