How to avoid "save as" prompt when remotely downloading file via SauceLabs - angularjs

Question

A protractor spec running from a Jenkins job, that connects to SauceLabs. It clicks a button to download a PDF, and checks that the file successfully downloaded. I am unable to get the chrome browser to NOT open a "Save As" prompt using an absolute path. I AM able to avoid the "Save As" prompt if I use '~/Downloads' as filename, but then my browser.wait that waits for the file to exist hangs forever.
// spec.js
import fs from 'fs'
import path from 'path'
fs.mkdirSync('./downloads')
describe('Clicking DOWNLOAD button', () => {
it('should download a proposal', () => {
const filename = path.resolve(__dirname, './downloads/proposal.pdf')
if (fs.existsSync(filename)) {
fs.unlinkSync(filename)
}
page.downloadProposalBtn.click()
browser.wait(() => fs.existsSync(filename), 180000)
.then(() => {
expect(fs.existsSync(filename)).toBe(true)
})
}, 180000)
})
Below is the relevant portion of my conf file. I would expect the prompt_for_download setting to make the prompt not show, but it does..
// conf.js
capabilities: {
platform: 'macOS 10.12',
browserName: 'chrome',
version: '59.0',
screenResolution: '1400x1050',
chromeOptions: {
args: ['--no-sandbox', '--test-type=browser', 'disable-infobars=true'],
prefs: {
download: {
prompt_for_download: false,
directory_upgrade: true,
default_directory: path.resolve(__dirname, './downloads'),
},
credentials_enable_service: false,
},
},
},
Am I missing something? I feel like I might be misunderstanding where Saucelabs is running these tests from, but it would seem that given I fs.mkdir the ./downloads folder, then when I path.resolve it, that should work.

Answer 1

Unsure if this constitutes an "answer" but this is how I'm proceeding. After a lot of research I think that testing if a file downloaded on a remote VM (like SauceLabs) isn't possible. What I am doing instead is breaking the test into two parts:
Test the download button: click the button and assert that no error occurred
Make GET request to the underlying endpoint api/download that the button is using, write the response to a folder, and from there assert (using nodejs) that the file exists in my Jenkins project's workspace. This feels hacky, but given SauceLabs doesn't seem to give much access to the VM that the webdriver is running on, I don't see another way.

Answer 2

You will get the prompt, even though the option is set to "false" if the default download directory doesn't exist. "./downloads" is OSX syntax, which the chrome driver probably doesn't understand.
Try this instead:
default_directory: __dirname + '/downloads'