Inconsistent `jest.fn()` behavior

[sparten11740]

When using jest.fn() from jest with a mocked implementation, the call count is eagerly updated and can be asserted against inside the implementation callback. The exodus-test implementation of jest.fn() does not do that as it depends on node's mock.fn() which only updates the call count after the callback returns.

To demonstrate the issue, the below logs a call count of 0:

import { mock } from 'node:test'

const mockedFn = mock.fn(() => {
  console.log(mockedFn.mock.callCount())
})

mockedFn()

The following (using jest's impl) however logs a call count of 1:

const mockedFn = jest.fn(() => {
  console.log(mockedFn.mock.calls.length)
})

mockedFn()

[ChALkeR]

Ah, jest also supports { type: 'incomplete', value: undefined } results

[ChALkeR]

This is documented here:

test/tests/jest/mock.test.js

Lines 102 to 110 in 5709f37

	// jest is actually failing on this, we follow node:test in pure impl
	test('calls are not counted prior to finish', () => {
	const f = jest.fn(() => f.mock.calls.length)
	expect(f()).toBe(0)
	expect(f(2)).toBe(1)
	expect(f()).toBe(2)
	expect(f.mock.calls.length).toBe(3)
	expect(f.mock.calls).toEqual([[], [2], []])
	})