Mutation testing doesn't work with Django app structure - import path issues ?

[arihantdaga]

Description
I'm trying to use mutmut with a Django project but running into issues with path resolution and import paths.
Project structure

my_project/
├── kiosk/
│   ├── __init__.py
│   ├── services/
│   │   ├── __init__.py
│   │   └── kiosk_payment_service.py  # Source to mutate
│   └── tests/
│       └── services/
│           └── test_kiosk_payment_service.py  # Tests
├── mutants/  # Created by mutmut
│   └── kiosk/
│       └── services/
│           └── kiosk_payment_service.py  # Mutated code
├── setup.cfg
└── pyproject.toml

Issue 1: File not found with relative path

Configuration:

[mutmut]

paths_to_mutate=kiosk/services/kiosk_payment_service.py

tests_dir=kiosk/tests/services/test_kiosk_payment_service.py

debug=true

Error:

ERROR: file or directory not found: kiosk/tests/services/test_kiosk_payment_service.py

This happens because mutmut runs pytest from inside the mutants/ directory, so kiosk/tests/... doesn't exist there.

Issue 2: Tests pass but mutations not detected

Configuration (using ../ to fix path):

[mutmut]
paths_to_mutate=kiosk/services/kiosk_payment_service.py

tests_dir=../kiosk/tests/services/test_kiosk_payment_service.py

debug=true

Result:

========= 64 passed in 10.75s ==========

exit code 0

Stopping early, because we could not find any test case for any mutant.

It seems that the selected tests do not cover any code that we mutated.

The tests run successfully, but mutmut reports no coverage of mutated code.

What I've tried

1. Using also_copy to include init.py files — didn't help
2. Various path configurations — same results

Question

Is there a recommended way to use mutmut with Django projects? Should setup_source_paths() be extended to handle arbitrary paths_to_mutate values?

Environment

• Python: 3.11
• mutmut: 3.4.0
• Django: 4.2
• OS: macOS

[Otto-AA]

Hi, I think mutmut should be able to handle this app structure. If you make a MRE I probably have time to test it on the weekend.

paths_to_mutate=kiosk/services/kiosk_payment_service.py

paths_to_mutate needs to point to all of your necessary source code, not only the code that you want to be mutated. Try to set this to paths_to_mutate=kiosk/ and then run with mutmut run kiosk.services.kiosk_payment_service*. See #414 for more information.

I would try to leave tests_dir empty in your case, not sure if it's necessary.

This happens because mutmut runs pytest from inside the mutants/ directory, so kiosk/tests/... doesn't exist there.

Yes, with the right config mutmut should copy all necessary source code + test code to the mutants/ directory and then run pytest in there. It basically makes a copy of your project (reduced to necessary files), but with mutated source code.

You want something like this:

my_project/
├── kiosk/
│   ├── __init__.py
│   ├── services/
│   │   ├── __init__.py
│   │   └── kiosk_payment_service.py  # Source to mutate
│   └── tests/
│       └── services/
│           └── test_kiosk_payment_service.py  # Tests
├── mutants/  # Created by mutmut
 |    ├── setup.cfg
 |    ├── pyproject.toml
 |    ├── kiosk/
│   ├──── __init__.py
│   ├──── services/
│   │      ├─── __init__.py
│   │      └─── kiosk_payment_service.py  # Mutated source code
│   └─── tests/
│       └─── services/
│           └─── test_kiosk_payment_service.py  # Tests
├── setup.cfg
└── pyproject.toml