Migrating Service Worker Tests to WPT


Unifying and improving divergent test forks for the benefit of all.

The Google Chrome team wrote a large set of valuable tests for a new web standard. The team asked us to move them to a place where more people could use and improve them.


The Google Chrome team had accumulated close to 100 tests for the developing Service Workers standard. They were authored to run within the Chromium infrastructure (Chromium is the open source project behind Google Chrome) and relied on non-standard features to varying degrees. Some included erroneous assertions based on outdated versions of the specification. Still others only offered partial coverage of the functionality under test.


We worked to transfer these tests to the Web Platform Tests project, where they would be consumed and maintained by many browser makers. This involved, verifying specification compliance, removing non-standard code, re-formatting code, and improving general coverage and thoroughness. Throughout this process, we took special care to preserve test coverage within the Chromium project.


By extending the Web Platform Tests project with Chromium’s tests, we helped other browser makers discover incompatibilities in their own implementations. We reported some of these to both Chromium and Firefox, and we expect that more were identified in the closed-source Safari and Edge projects. We also reported issues with the Service Workers specification itself and submitted patches for various editorial problems.

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