add tests for Promise.withResolvers proposal

[peetklecha]

This shouldn't be merged yet as Promise.withResolvers is still only Stage 2.

[peetklecha]

Now Stage 3.

[ptomato]

Thanks for contributing this! Would you mind opening a tracking issue? An example is #3756. You don't have to write the whole testing plan, someone else can help with that, but we should use one to verify that we're covering everything in the proposal.

I haven't looked too closely at this PR yet so I might be missing something, but it seems like there are some cases particularly with subclassing Promise that aren't yet tested.

We also need to add the standard boilerplate tests for built-in APIs. For an example, see length.js, name.js, prop-desc.js, not-a-constructor.js, builtin.js in https://github.com/tc39/test262/tree/main/test/built-ins/Array/fromAsync.

We don't have to block reviewing and merging this PR on complete coverage, the other tests can come in following PRs, but we should keep track in the tracking issue of what's been merged.

[syg]

Could we have this merged soon for shipping in Chrome?

[peetklecha]

sorry for the delay with this.

• i've now addressed all the comments i've recieved
• there's a failing test from circle/ci which wasn't there before and which i don't understand, any help with it would be appreciated
• per @ptomato 's request i've created an issue to track full test coverage of Promise.withResolvers: Tests for Promise.withResolvers #3910

[ptomato]

Thanks, @peetklecha. The failing CI job is #3891, we really should remove the job until that's fixed. I'll merge this now, and add some suggestions to the tracking issue you opened.