Vendoring Puppeteer

As mentioned in the chapter on Testing, we run the full Puppeteer test suite on try. These tests are vendored in central under remote/test/puppeteer/ and we have a script to pull in upstream changes.

We periodically perform a manual two-way sync. Below is an outline of the process interspersed with some tips.

  1. Clone the Puppeteer git repository and checkout the release tag you want to vendor into mozilla-central.

     % git checkout tags/v10.0 -b sync-v10.0
  2. Apply any recent changes in remote/test/puppeteer to the Puppeteer branch created above.

    You might want to [install the project] at this point and make sure unit tests pass. Check the project’s package.json for relevant testing commands.

    You should use this as basis for a PR to the Puppeteer project once you are satisfied that the two-way sync will be successful in mozilla-central. See their

    Typically, the changes we push to Puppeteer include unskipping newly passing unit tests for Firefox along with minor fixes to the tests or to Firefox-specific browser-fetching and launch code.

    Be sure to run tests against both Chromium and Firefox in the Puppeteer repo. You can specify your local Firefox build when you do so:

     % BINARY=<path-to-objdir-binary> npm run funit
  3. Now back in mozilla-central, you can run the following mach command to copy over the Puppeteer branch you just prepared. The mach command has flags to specify a local or remote repository as well as a commit.

     % ./mach remote vendor-puppeteer

    By default, this command also installs the newly-pulled Puppeteer package in order to generate a new package-lock.json file for the purpose of pinning Puppeteer dependencies for our CI. There is a --no-install option if you want to skip this step; for example, if you want to run installation separately at a later point.

  4. Go through the changes under remote/test/puppeteer/test and unskip any newly-skipped tests (e.g. change itFailsFirefox to it). A mass-change with awk might be useful here.

    Why do we do this? The Puppeteer team runs their unit tests against Firefox in their CI with many tests skipped. In contrast, we leave these tests unskipped in Mozilla CI and track test expectation metadata in puppeteer-expected.json instead.

  5. Use ./mach puppeteer-test (see Testing) to run Puppeteer tests against both Chromium and Firefox in headless mode. Again, only running a subset of tests against Firefox is fine – at this point you just want to check that the typescript compiles and the browser binaries are launched successfully.

  6. Next you want to update the test expectation metadata: test results might have changed, tests may have been renamed, removed or added. The easiest way to do this is to run the Puppeteer test job on try (see Testing). You will find the new test metadata as an artifact on that job and you can copy it over into your sync patch if it looks reasonable.

    Examine the job logs and makes sure the run didn’t get interrupted early by a crash or a hang, especially if you see a lot of TEST-UNEXPECTED-MISSING in the Treeherder Failure Summary. You might need to add new test skips or fix some new bug in the unit tests. This is the fun part.

  7. Once you are happy with the metadata and are ready to submit the sync patch up for review, run the Puppeteer test job on try again with --rebuild 10 to check for stability.