Basic Selenium Webdriver Code

var webdriver = require('selenium-webdriver');

// Input capabilities
var capabilities = {
  'browserName' : 'Chrome',
  'browser_version' : '43.0',
  'os' : 'Windows',
  'os_version' : '7',
  'resolution' : '1024x768',
  'browserstack.user' : '<username>',
  'browserstack.key' : '<access_key>',
  'browserstack.local' : true,
  'browserstack.debug' : true,
  'build' : 'BS Test case',
  'name' : 'Test With Local',
  'project' : 'BS Test case'
}

var driver = new webdriver.Builder().
  usingServer('http://hub.browserstack.com/wd/hub').
  withCapabilities(capabilities).
  build();

driver.get('<Your_URL>');

var WAIT_TIME = 5000;
return driver.sleep(WAIT_TIME).then(function() {
var fs = require('fs');

webdriver.WebDriver.prototype.saveScreenshot = function(filename) {
    return driver.takeScreenshot().then(function(data) {
        fs.writeFile(filename, data.replace(/^data:image\/png;base64,/,''), 'base64', function(err) {
            if(err) throw err;
        });
    })
};

driver.saveScreenshot('scr_with_local.png');
driver.quit();
});