iOS XCtest accessing App View Controllers/UI

I am new to iOS development. I want to write unit tests for an app which uses an SDK where the authenticate method is of the form:

(void)authenticate:(UIViewController *)presentingViewController clearCookies:(BOOL)clearCookies completionBlock:(AuthCompletionBlock)completionBlock.

To authenticate the user, an embedded web browser needs to open in the UIViewController(passed in the method parameters) . Can the unit tests access app UI? How do I make sure that the browser opens, user authenticates thru app UI and then the unit tests execute.