`jest-fake-timers` breaks `util.promisify(setTimeout)`

[GeorgeBekh]

🐛 Bug Report

Jest breaks util.promisify(setTimeout) functionality when using fake timers.
When running code with jest-fake-timers it doesn't have the field setTimeout[util.promisify.custom], even in jest-environment-node (jest-environment-jsdom correctly doesn't have it).

(Updated description to refer to the specific jest-fake-timers problem)

envinfo

  System:
    OS: Linux 4.19 Netrunner 19.08 (Indigo)
    CPU: (12) x64 Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz
  Binaries:
    Node: 12.12.0 - /bin/node
    npm: 6.12.0 - /bin/npm
  npmPackages:
    jest: ^24.9.0 => 24.9.0

[SimenB]

The provided reproduction passes for me

Can you set up repl.it, codesandbox or a repository showing the error?

[GeorgeBekh]

Sure

https://codesandbox.io/s/determined-chandrasekhar-jfey6?fontsize=14
In the right bottom select terminal, click the "Plus" button and run npm run test

[GeorgeBekh]

@SimenB

[jeysal]

Confirmed that setTimeout[util.promisify.custom] is missing in jest-environment-jsdom. But it is there in jest-environment-node. I think this is correct? Most environments with a DOM (browsers) will not have this either, only Node will.
However, it should definitely be there in jest-environment-node when using jest.useFakeTimers() - we should make sure jest-fake-timers supports that.

[SimenB]

Ah, I just tested with node. But yeah, util.promisify won't work for the timer in jsdom

[jeysal]

@GeorgeBekh that should clarify for your case, see docs on how to use different test environments. We could change this issue to be about jest-fake-timers missing the property though :)

[GeorgeBekh]

Thanks I've forgot, about the testEnvironment option.
@jeysal, sure. I'm glad I've helped somehow :)

[jeysal]

updated title/description :)