pytest import file mismatch error: how to fix

TL;DR

This error means two test files (or a test file and a source file) share the same basename, like tests/a/utils.py and tests/b/utils.py, and neither directory has an __init__.py, so pytest cannot tell them apart as modules. Fix it by adding __init__.py files to make packages explicit, by renaming one file, or by setting --import-mode=importlib so pytest imports by file path instead of by guessed module name.

The query

pytest import file mismatch error: how to fix

Use this when

• pytest aborts during collection with "import file mismatch".
• You added a new test directory and collection broke.

Not for

• ModuleNotFoundError for a real dependency; that is a different problem.
• Coverage or plugin configuration issues.

Steps

1. Read the full error; pytest names both colliding files. Expected output: you see the two paths with the same basename.
2. Check whether their directories contain __init__.py. Expected output: you know which dirs are plain directories vs packages.
3. Add __init__.py to the test directories (or rename one of the colliding files). Expected output: basenames now resolve to distinct module paths.
4. Alternatively, run with pytest --import-mode=importlib and re-run. Expected output: collection succeeds without the mismatch.
5. Re-run the full suite to confirm nothing else collided. Expected output: collection completes, tests run.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstktd6iQssg2ya5aQvPAT8A