Choosing Project Options

I have a new iMac so I installed version 7.1.1(7B1005). When creating the Random Password project there two new checkable items below Use Core Data. They are Include Unit Tests and Include UI Tests. I left them checked but what is the meaning of each?

I think there must be some changes to this version of xcode. While working on the project the changes to the swift code fail to compile. I get the same error if I copy and past the solution .

var mainWindowController: MainWindowController?                        <----- I get use of undeclared MainWindowController

func applicationDidFinishLaunching(aNotification: NSNotification) {
    // Create a window controller with a XIB file of the same name
    let mainWindowController = MainWindowController()
    // Put the window of the window controller on screen
    // Set the property to point to the window controller
    self.mainWindowController = mainWindowController