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Google Summer of Code 2024 Final Report

Introduction

I am excited to share the final report of my Google Summer of Code (GSoC) experience with PyBaMM, a project under the NumFOCUS umbrella. Over the past few months, I have worked on modernizing and enhancing PyBaMM’s testing infrastructure. This report will summarize the progress made during the program and highlight key accomplishments and learnings.

Project Overview

PyBaMM (Python Battery Mathematical Modelling) is an open-source tool for simulating battery models, offering a flexible and modular framework for interdisciplinary research. My GSoC project aimed to improve PyBaMM’s testing infrastructure by migrating existing tests from unittest to the more modern and efficient pytest framework. This migration included optimizing test execution and implementing advanced pytest features.

Key Achievements

  • Migration to Pytest

  • Initial Steps: Early in the project, we set up pytest to run existing unittest style tests. The transition allowed us to leverage pytest’s parallel test execution capabilities using the pytest-xdist plugin, which significantly improved test execution speed.

  • Integration Tests: We successfully ran integration tests with pytest. A major challenge was handling parallel execution of integration tests that involved writing to the same JSON file. To resolve this, we used unique UUIDs for filenames, which eliminated race conditions. Infrastructure Improvements

  • Removal of run-tests.py: We deprecated the legacy run-tests.py file in favor of using nox, a tool for automating testing in multiple Python environments. This streamlined our testing process and removed redundant code.

  • Switch to src Layout: We transitioned from a flat project layout to a src layout. This change facilitated better testing of built wheels using cibuildwheel, a tool for creating Python Wheels. The src layout ensured that the wheel and project directory did not conflict during testing. Test Migration and Optimization

  • Migrating Tests: We migrated a significant number of tests from unittest to pytest, converting around 100 files in total. The process involved using tools like pytestify for syntactical conversion and manual adjustments for complex cases.

  • Handling Non-Deterministic Tests: We replaced a custom TestCase file used for handling non-deterministic tests with pytest fixtures, improving the stability and reliability of test results. Enhanced CI/CD Integration

  • GitHub Actions Annotations: We integrated pytest-github-actions-annotate-failures to annotate test failures directly in the GitHub Actions UI, making it easier to diagnose issues without sifting through lengthy logs.

  • Testing Wheels with cibuildwheel: We tested wheels in the CI pipeline to ensure their compatibility and functionality, using pytest markers to streamline this process.

Final Steps and Future Work

  • Completion of Pytest Migration: We finalized the migration of all tests to pytest, completing the main objective of the project. This included moving the remaining files and implementing pytest’s advanced features such as fixtures and parameterization.

  • Future Improvements: Looking ahead, potential improvements include further optimization of the pytest migration tool (pytestify) and exploring additional pytest features to enhance test coverage and efficiency.

Conclusion

My time as a GSoC student working with PyBaMM has been incredibly rewarding. The project not only provided me with valuable experience in modernizing a large codebase but also deepened my understanding of testing frameworks and continuous integration practices. I am grateful for the support and guidance from the PyBaMM community and look forward to continuing my contributions to the project.

Thank you for following along with my GSoC journey. For more details on the specific changes and contributions, you can refer to the associated pull requests and documentation on the PyBaMM GitHub repository.