[jwcastillo]

Your checklist for a pull request to sitespeed.io

Please review the guidelines for contributing to this repository.

• I'm making a big change or adding functionality so I've already opened an issue proposing the change to other contributors, so I got feedback on the idea before took the time to write precious code (small fix; the issue is Unknown --browsertime.connectivity.engine values are accepted silently, and -c in Docker does not throttle without a warning #4923)
• Check that your change/fix has corresponding unit tests (if applicable)
• Squash commits so it looks sane
• Update the documentation https://github.com/sitespeedio/sitespeed.io/tree/main/docs in another PR (not needed: behavior now matches the documented choices)
• Verify that the test works by running npm test and test linting by npm run lint

Description

Fixes part 1 of #4923.

--browsertime.connectivity.engine declares choices: ['external', 'throttle', 'humble'], but any value was accepted and the run silently used no throttling with exit code 0 (for example --browsertime.connectivity.engine tc). This adds the check to validateInput, so an unknown value now fails with:

Error: Unknown connectivity engine "tc". Choose one of: external, throttle, humble.

Tests: new CLI test CLI should reject an unknown connectivity engine (fails without the change, passes with it). npx ava: 98 tests passed. npx eslint on the changed files: no issues.

The second part of the issue (warning when a profile is set but the engine is external, the default inside Docker) changes behavior, so I left it for discussion in the issue.

This pull request was made with assistance from Claude.

[soulgalore]

Thank you @jwcastillo