Using Alamofire in UI Test Target

Question

The below code snippet using Alamofire works fine in iOS app but the code does not work in iOS UI Testing target.

let configuration = NSURLSessionConfiguration.defaultSessionConfiguration()
configuration.HTTPAdditionalHeaders =   Alamofire.Manager.defaultHTTPHeaders
manager = Alamofire.Manager(configuration: configuration)
manager!.request(.GET, "https://www.google.com")
        .responseString { response in
            print(response.request)  // original URL request
            print(response.response) // URL response
            print(response.result)   // result of response serialization
            print("HTML: \(response.result.value)")
    }

The completion handler never gets invoked in UI Testing target.

If I add .progress block to request, that is getting executed, but the completionHandler still does not get executed.

Can someone please shed light on what I might be doing wrong.