Add tests for Temporal.now.timezone

[jugglinmike]

In service of gh-3002

/cc @ptomato @Ms2ger

[Ms2ger]

Suggested change

	assert.sameValue(isConstructor(Temporal.now.timeZone), false, 'isConstructor(Math.min) must return false');
	assert.sameValue(isConstructor(Temporal.now.timeZone), false, 'isConstructor(Temporal.now.timeZone) must return false');

[jugglinmike]

Whoops! Thanks

[Ms2ger]

Suggested change

	assert(Object.isExtensible(Temporal.now.timeZone));
	assert.sameValue(Object.isExtensible(Temporal.now.timeZone), true);

[jugglinmike]

This looks equivalent to me. Could you say a little about why we ought to use assert.sameValue instead of assert?

[Ms2ger]

I understood the former to be preferred in test262, but I may be misremembering. Happy to go either way.

[rwaldron]

@jugglinmike you're right, this is fine as is.

@Ms2ger assert() is discouraged in cases such as assert(foo === "something interesting"), which is better written as assert.sameValue(foo, "something interesting") because you'll get a more meaningful error message.

[Ms2ger]

Sounds like I misremembered, thanks for the clarification. I couldn't find this discouragement in the documentation at https://github.com/tc39/test262/blob/main/CONTRIBUTING.md#test-environment - could you add it?

[rwaldron]

This test just tell me that those two things are the same thing, but explicitly that either of them is an instance of Temporal.TimeZone.

assert(Temporal.now.timeZone() instanceof Temporal.TimeZone)?

[jugglinmike]

The instanceof operator has a lot of additional semantics which would make this test less precise. For example, it would be satisfied if the return value was an instance of a subclass of Temporal.TimeZone. I believe a strict equality check is the most precise way to verify this behavior.

[Ms2ger]

We could have both?

[rwaldron]

Rebased locally and merged