= Improving Interop with WPT 
''by Philip Jägenstedt & Stephen McGruer'' 

- Why does interop matter?
    - Users, developers, browser engines
    - Users
        - Go to website on favorite browser, but broken
        - Go find a browser it’s meant to work on
        - All the things we do for interop make our lives easier
    - Developers
        - MDN ran largest survey ever
        - Top pain points cross-browser compat/interop/testing
        - What to do?
- A shared test suite, for all the web
    - 20 commits from WebKit
    - Believe it is infrastructure
- High Level View
    - Chrome + Firefox + Safari
    - 0/3 ~ 5K tests
    - 1/3 ~ 6K tests
    - 2/3 ~ 6K tests
    - 3/3 ~ 20K tests
    - Moving to target the browser specific failures (2/3)
    - Interop is steady
- Browser specific failures in WPT
    - Gap is growing
    - Methodology for data for this presentation
    - WPT splits into tests and sub-tests
        - Sub-tests are within the test file
        - Some tests with too many subtests
        - Encoding tests have absurd
        - Normalized to test level
- Runs on Azure pipelines
    - STP runs every 3 hours, takes < 2 hours
    - Edge Dev and Canary too
    - Thanks Microsoft and @mustjab
- Runs on Taskcluster
    - Chrome + Firefox on every commit
    - WebKitGTK ally
    - Thanks Mozilla and @jgraham
- Room for Improvement
    - STP updates
    - Reliability
    - Thanks Apple and @burg
    - https://github.com/web-platform-tests/wpt/projects/4
- Epiphany / WebKit
    - Also run subtests on Linux for a second opinion
- WebKit on Linux
    - Google partnering with Igalia
    - WebKitGTK stable+nightly runs
    - Fixing noise in the data
- 2-way Sync
    - Script for WebKit exists
- 2-way Sync in Chromium
    - Update impl+tests in single review
    - Use of WPT by Chromium devs up ~220% (*j.mp/wpt-yes)
    - ~55% of impl+test changes now use WPT
        - Chromium & Gecko
            - Automatic import
            - Automatic export AFTER changes land
        - WebKit
            - Manual import (?)
                - Yes it is
            - Manual (?) export BEFORE changes land
    - Room for improvement / collaboration?
    - Issue on export PRs?
- A Wishlist
    - Collaborate on wit.fyi
        - Wish there was a way to browser-specific failures in the same way computed for the graph
    - Running web-driver to internal builds
    - Collaborate on running WPT on iOS
    - Collaborate on MDN survey: developers say interop is a big thing

- WPT Right approach
    - Importing all the tests could slow us down
    - Maybe keep them separate?
    - New tests added don’t look like regressions
    - WPT: Tracking WPT as a sub-module is not compatible

- Please don't scrape wpt.fyi, use the [https://github.com/web-platform-tests/wpt.fyi/blob/master/api/README.md API]