Move sawtooth test references to references.json (#1762)

[akshat3410]

Summary

Moves hardcoded sawtooth test reference values from sawtooth_model_test.py to the centralized references.json file, making them auto-regeneratable via the regenerate_torax_refs.py script.

Closes #1762

Changes Made

1. Extended regenerate_torax_refs.py

• Added _calculate_sawtooth_crash_references() function
• This function runs a full simulation step to trigger sawtooth crash
• Captures post-crash T_e, n_e, and psi profiles
• Modified main() to route sawtooth case to this special function

2. Updated torax_refs.py

• Added sawtooth_references() function with sawtooth-specific config
• Registered in REFERENCES_REGISTRY for auto-regeneration
• Includes proper error handling for missing JSON data

3. Modified sawtooth_model_test.py

• Load post-crash reference values from JSON instead of hardcoded constants
• Removed 38 lines of hardcoded numpy arrays (_POST_CRASH_TEMPERATURE, _POST_CRASH_N, _POST_CRASH_PSI)
• Added JSON loading in setUp() method

4. Updated references.json

• Added sawtooth_references entry with generated post-crash values

Testing

• All sawtooth tests pass: pytest torax/_src/mhd/sawtooth/tests/sawtooth_model_test.py -v
• Verified test assertions use generated values correctly
• References can be regenerated with the script (when dependencies are available)

Future Usage

When the sawtooth model changes, developers can regenerate the test references automatically instead of manually editing arrays:

python -m torax.tests.scripts.regenerate_torax_refs \
    --case=sawtooth_references \
    --write_to_file

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[tamaranorman]

Adding these to the script is good but can they be in a separate file next to the relevant tests

And then if you can sign the CLA so we can run the tests

[akshat3410]

Sure, I’ll make the changes exactly as you requested — I’ll move the additions into a separate file next to the relevant tests and update the imports accordingly. I’ll push the updated commit shortly.

[jcitrin]

Please fix failing tests

[akshat3410]

I'll Fix it right away.

[akshat3410]

@jcitrin Fixed! Rebased to latest main, updated the API call, and regenerated references. All 3 tests pass locally. Please approve the workflow run. Thanks!

[jcitrin]

Please see test errors and fix.

[akshat3410]

I'll Fix it right away.