How to get nightwatch test_workers work with browserstack-local - nightwatch.js

Question

I am trying to get Nightwatch's inbuilt parallel test_workers working with browserstack-local for local url testing.
When running tests without browserstack local, Nightwatch test_workers seem to work just fine. The same is true for running local tests without test_workers enabled.
I have tried the examples found here https://github.com/browserstack/nightwatch-browserstack but none of these uses browserstack-local in combination with Nightwatch test_workers.
When running locally with test_workers I get the following output.
Connecting local
Connected. Now testing...
Process terminated with code 0.
Has anyone else encountered similar issues?
EDIT: I have since resolved this issue and have posted an answer below
I have dumped the relevant configuration files below.
My local.conf.js
nightwatch_config = {
globals_path: 'globals.js',
output_folder: false,
src_folders: ['tests'],
selenium: {
'start_process': false,
'host': 'hub-cloud.browserstack.com',
'port': 80
},
test_workers: {
"enabled": true,
"workers":2
},
test_settings: {
default: {
desiredCapabilities: {
'browserstack.user': process.env.BROWSERSTACK_USER,
'browserstack.key': process.env.BROWSERSTACK_ACCESS_KEY,
'browserstack.local': true,
'browserstack.debug': false,
}
}
}
};
// Code to copy seleniumhost/port into test settings
for (let i in nightwatch_config.test_settings) {
if (nightwatch_config.test_settings.hasOwnProperty(i)) {
let config = nightwatch_config.test_settings[i];
config['selenium_host'] = nightwatch_config.selenium.host;
config['selenium_port'] = nightwatch_config.selenium.port;
}
}
module.exports = nightwatch_config;
local.runner.js
#!/usr/bin/env node
var Nightwatch = require('nightwatch');
var browserstack = require('browserstack-local');
var bs_local;
process.env.BROWSERSTACK_ID = new Date().getTime();
try {
process.mainModule.filename = "./node_modules/.bin/nightwatch";
// Code to start browserstack local before start of test
console.log("Connecting local");
Nightwatch.bs_local = bs_local = new browserstack.Local();
bs_local.start({ 'key': process.env.BROWSERSTACK_ACCESS_KEY }, function (error) {
if (error) throw error;
console.log('Connected. Now testing...');
Nightwatch.cli(function (argv) {
Nightwatch.CliRunner(argv)
.setup(null, function () {
// Code to stop browserstack local after end of parallel test
bs_local.stop(function () { });
})
.runTests(function () {
// Code to stop browserstack local after end of single test
bs_local.stop(function () { });
});
});
});
} catch (ex) {
console.log('There was an error while starting the test runner:\n\n');
process.stderr.write(ex.stack + '\n');
process.exit(2);
}
and my package.json script
node ./local.runner.js -c ./local.conf.js

Answer 1

The issue here was due to the module filename being incorrectly defined in the local.runner.js
process.mainModule.filename = "./node_modules/.bin/nightwatch";
should be pointed directly at the Nightwatch file in its directory.
process.mainModule.filename = "./node_modules/nightwatch/bin/nightwatch";
The difference in these files and the exact reason for this solution working are beyond me.
The answer was derived from the "suite" runner in https://github.com/browserstack/nightwatch-browserstack

Answer 2

It seems you are not specifying browsers. Modify your configuration file to be inline with the following configuration file:
var browserstack = require('browserstack-local');
nightwatch_config = {
src_folders : [ "local" ],
selenium : {
"start_process" : false,
"host" : "hub-cloud.browserstack.com",
"port" : 80
},
test_workers: {
"enabled": true,
"workers":2
},
common_capabilities: {
'browserstack.user': process.env.BROWSERSTACK_USERNAME || 'BROWSERSTACK_USERNAME',
'browserstack.key': process.env.BROWSERSTACK_ACCESS_KEY || 'BROWSERSTACK_ACCESS_KEY',
'browserstack.debug': true,
'browserstack.local': true
},
test_settings: {
default: {},
chrome: {
desiredCapabilities: {
browser: "chrome"
}
},
firefox: {
desiredCapabilities: {
browser: "firefox"
}
},
safari: {
desiredCapabilities: {
browser: "safari"
}
}
}
};
// Code to support common capabilites
for(var i in nightwatch_config.test_settings){
var config = nightwatch_config.test_settings[i];
config['selenium_host'] = nightwatch_config.selenium.host;
config['selenium_port'] = nightwatch_config.selenium.port;
config['desiredCapabilities'] = config['desiredCapabilities'] || {};
for(var j in nightwatch_config.common_capabilities){
config['desiredCapabilities'][j] = config['desiredCapabilities'][j] || nightwatch_config.common_capabilities[j];
}
}
module.exports = nightwatch_config;