Best way of testing OAuth response in iOS WebView?

I am new to testing for iOS mobile application. My scenario is, I have a url when I raise the url request the response is webview its basically oauth response. Now i want to test the that web view by feeding user name and password through either unit testing or UIAutomation testing. Kindly guide me the best ways to achieve it.

PFA of sample webview page

So required solution is, I need to give both valid and invalid parameters and need to check the response in testing environment. I hope its clear to answer. Still need any clarification kindly comment it over here.

Thank you for all in advance....