Add supprot for AbortSignal

Fetch request can be cancelled through AbortController API & cross-fetch library used here is wrapper around node-fetch library which does support it

It would be really helpful if AbortController was exposed by this library to allow testing cases where requests may be cancelled.

[akmjenkins]

Those are coming from cross-fetch, not jest-fetch-mock. More importantly, those are part of the specification that need to be supplied by fetch. An AbortController is more generic and, while fetch can make use of an AbortController (by listening to it’s signal), it’s not required for fetch to function (unlike Headers, Response, and Request).

I still fail to see the use case - if you want to test an aborted fetch, then you should already have an implementation of AbortController. Right now jest-fetch-mock still doesn’t support testing aborted fetches, but this is just me advocating for my PR 😄

[Gozala]

@Gozala I’m probably missing something, but shouldn’t your AbortController instance come from the code your testing, not the testing library?

@akmjenkins if fetch, Headers, Response, Request all come from here I would expect AbortController to do the same

https://github.com/jefflau/jest-fetch-mock/blob/454fcc956de67175567ced958c28b0c33bbd0f10/src/index.js#L49-L52