doc(contributing): add info on bisecting upstream changes (#6402)

Co-authored-by: Johan Bay <jobay@google.com>
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Mathias Bynens 2020-09-08 15:19:37 +02:00 committed by GitHub
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@ -279,7 +279,15 @@ The following steps are needed to update the Chromium version.
1. Update `src/revisions.ts` with the found revision number.
1. Run `npm run ensure-correct-devtools-protocol-revision`.
If it fails, update `package.json` with the expected `devtools-protocol` version.
1. Run `npm run tsc` and `npm install` and ensure that all tests pass. If a test fails, bisect the upstream cause of the failure, and either update the test expectations accordingly (if it was an intended change) or work around the changes in Puppeteer (if its not desirable to change Puppeteers observable behavior).
1. Run `npm run tsc` and `npm install` and ensure that all tests pass. If a test fails, [bisect](#bisecting-upstream-changes) the upstream cause of the failure, and either update the test expectations accordingly (if it was an intended change) or work around the changes in Puppeteer (if its not desirable to change Puppeteers observable behavior).
### Bisecting upstream changes
Sometimes, performing a Chromium roll causes tests to fail. To figure out the cause, you need to bisect Chromium revisions to figure out the earliest possible revision that changed the behavior. The script in `utils/bisect.js` can be helpful here. Given a Node.js script that calls `process.exit(1)` for bad revisions, run this from the Puppeteer repositorys root directory:
```sh
node utils/bisect.js --good 686378 --bad 706915 script.js
```
## Releasing to npm