Follow up from #240, we need a cookbook example that does this:

Create an object that supports exactly the same interface as Temporal and is indistinguishable from it (even though side-door means such as Function.prototype.toString) except that it provides no mechanism by which code could use it to determine that the host environment is not executing within a date, time, time zone, and tzdata edition under the control of the creator, without costing the creator any capabilities provided by the native Temporal. This has use for secure environments like SES, but also for purely functional environments like Elm (cf. #103) and for testing.

This is probably best done after support for custom time zones and calendars are added to the polyfill.