javascript - Promise not being resolved when run inside Jasmine unit tests -

facing strange issue when testing method returns promise in jasmine unit tests. have following class:

import http = require('http'); import https = require('https'); import fs = require('fs');  export default class imagedownloader {     constructor(protected downloadpath:string) {}      async download(url: string): promise<string> {         return new promise<string>((resolve, reject) => {             let file = fs.createwritestream(this.downloadpath, { autoclose: true });             let schema:any = url.startswith('https') ? https : http;              schema.get(url, (response:fs.readstream) => {                 response.pipe(file).on('finish', () => resolve(this.downloadpath));             }).on('error', (error) => reject(error));         });     } } 

it downloads image download path given in constructor, , resolves promise download path once file has been written disk.

i've written jasmine unit test:

import fs = require('fs'); import http = require('http'); import imagedownloader '../../src/image/imagedownloader';  describe('image downloader', () => {     describe('download()', () => {         it('returns path downloaded image', done => {             spyon(http, 'get').and.callfake((url, cb) => {                 cb(fs.createreadstream(__dirname+'/../assets/elephpant.png'));             });              let imagedownloader = new imagedownloader('/tmp/image');              imagedownloader.download('http://foo.bar/bazz.jpg').then((path) => {                 expect(path).toequal('/tmp/image');                 done();             });         });     }); }); 

in test, mock node http module in order return own faked "http response". remember node's incomingmessage class (what returned response http.get()) implements readable stream interface, i'm returning own readable stream fs.createreadstream().

when running test, times out because promise never getting resolved:

f failures:  1) image downloader download() returns path downloaded image 1.1) error: timeout - async callback not invoked within timeout specified jasmine.default_timeout_interval. 

however, weird part if change part of download() method resolves promise this:

response.pipe(file).on('finish', () => console.log('the promise resolved here')); 

i see output:

the promise resolved here f failures:  1) image downloader download() returns path downloaded image 1.1) error: timeout - async callback not invoked within timeout specified jasmine.default_timeout_interval. 

so we're getting part when promise called. it's i'm calling resolve() promise not resolving reason.