Testing the state of promises in JavaScript without using Promise

Relevant posts:

• How to check if a Promise is pending [duplicate]
• How can I synchronously determine a JavaScript Promise's state?
• The chosen solution for this post

Use case: I would like to test a code with Jest that already uses promises, so to not mess up the promise queue, I needed a way to peek into the promise without using Promise.resolve or Promise.race.

My helper function:

const PROMISE_STATUS = Object.freeze({
	PENDING: 'pending',
	FULFILLED: 'fulfilled',
	REJECTED: 'rejected'
})

function promiseStatus(p) {
	if (inspect(p).includes(PROMISE_STATUS.PENDING)) {
		return PROMISE_STATUS.PENDING;
	}
	else if (inspect(p).includes(PROMISE_STATUS.REJECTED)) {
		return PROMISE_STATUS.REJECTED;
	}
	else {
		return PROMISE_STATUS.FULFILLED;
	}
}

Test for it with Jest:

test('promiseStatus', () => {
	expect(promiseStatus(new Promise(()=>{}))).toEqual(PROMISE_STATUS.PENDING);
	expect(promiseStatus(Promise.resolve(2))).toEqual(PROMISE_STATUS.FULFILLED);
	expect(promiseStatus(Promise.reject(0))).toEqual(PROMISE_STATUS.REJECTED);
})