How to mock ndjsonStream or ReadableStream in a jest test case

[kanteankit]

Hi guys,
Thank you for this awesome library.
I was wondering how I can write a test case that involves ndjsonStream.
Taking the example from the docs and modifying it a bit:

import ndjsonStream from "can-ndjson-stream";
var users = []
var getUsers = ()=>{ return fetch("/users") }

var fetchUsersList = ()=>{
          getUsers()
            .then( ( response ) => {
               return ndjsonStream( response.body ); //ndjsonStream parses the response.body

            } ).then( ( exampleStream ) => {
                const reader = exampleStream.getReader();
                let read;
                reader.read().then( read = ( result ) => {
                if ( result.done ) {
                  return;
                }

               users.push(result.value)  // Each json gets pushed to items array
               reader.read().then( read );
           } );
       } );
}

The code above calls getUsers that returns a Promise object. This Promise is then handled by ndjsonStream. Each JSON read by ndjsonStream is then pushed to the users array.
Now, I want to write a test case using jest that creates a mock function for getUsers and then checks whether the users list gets populated or not. Something like this:

let fakeUsersList = '{"id":"abcd","title":"Random User 1"}\n{"id":"pqrs","title":"Random User 2"}'
import 'isomorphic-fetch'
getUsers = jest.fn(()=>{

     return new Promise((resolve, reject)=>{
          resolve(new Response(fakeUsersList, {
                            status: 200,
                            statusText: 'OK,
                           headers: {
                               'Content-type': 'application/x-ndjson'
                            }
                        })
                   )
           })
})

it('should populate the user list',()=>{
    fetchUsersList()
   expect(users.length).toBe(2)
})

The above code basically says, when fetchUsersList is called, instead of calling the actual getUsers, call the dummy function that responds back with a Promise object. The fake Promise object resolves with a fakeUsersList. Then we test whether the users list has been populated or not

The problem I am facing is this:
I was able to create a dummy response for my API call using a Promise object and using isomorphic-fetch to create Response object.
But, I have no way to create a dummy ReadableStream object. When I run my test case, I get the error ReadableStream is not defined, when this line gets executed
ndjsonStream( response.body)

Is there a way to create a mock/dummy of either the ndjsonStream function itself or the ReadableStream object?
Thanks in advance for any help/suggestions that you guys could provide