If you guys are interested in this, you have some of the better tests in existence, and test262 would benefit from them greatly. Then hopefully stupid things like Safari's non-compliant implementations would not happen, because everybody would be running your tests :)

I'd love to help in any way I can to make this process more smooth, if you are up for it.

I am trying to blaze the trail with my Array.prototype.contains reference implementation: notably the package.json which configures the test runner, and the tests themselves. One big thing to notice is that test262 favors lots of small little files---more or less one for each Mocha it.

I imagine in the process you will find test262 to be pretty anemic compared to Mocha/Chai. In particular we currently do if (!condition) { $ERROR(msg); } instead of assert(condition, message). I think (@bterlson can correct me if I'm wrong) that putting together a basic assert library, containing e.g. assert, assertEqual, assertOwnPropertiesEqual or a few other things, would probably be OK. Maybe a good first step would be to figure out the minimum set of assertions you'd need, and if we agree on them, get them into test262 as helpers.

Also tagging in @smikes who has been doing great test262 work and can probably help advise.