RunTestsInCloud.cs

private string _username = "antonangelov2";
private string _authkey = "yxMDqyW62chvy3QycWRb";
private IWebDriver _driver;

[SetUp]
public void SetupTest()
{
    var caps = new DesiredCapabilities();
    caps.SetCapability("browserstack.debug", "true");
    caps.SetCapability("build", "1.0");

    caps.SetCapability("os", "Windows");
    caps.SetCapability("os_version", "8.1");
    caps.SetCapability("browser", "Firefox");
    caps.SetCapability("browser_version", "54.0");
    caps.SetCapability("resolution", "1366x768");
    caps.SetCapability("browserstack.video", "true");
            
    caps.SetCapability("build", "version1");
    caps.SetCapability("project", "AutomateThePlanet");

    caps.SetCapability("browserstack.user", _username);
    caps.SetCapability("browserstack.key", _authkey);

    _driver = new RemoteWebDriver(new Uri("http://hub-cloud.browserstack.com/wd/hub/"), caps, TimeSpan.FromSeconds(180));
}

[TearDown]
public void TeardownTest()
{
    _driver.Quit();
}