As announced at WWDC 2015, changes to Xcode 7 mean you no longer need to sign up to the Apple Developer Program to test your apps on your device.
From the Xcode 7 Release Notes:
Now you can go beyond the simulator to test your app on an iPad, iPhone, or Apple Watch — for free. Simply enter your Apple ID into the Accounts preference pane, then attach a device to your Mac using a Lightning cable. You can use the same Apple ID you already use for iCloud, iTunes, or the App Store, or create a new one. Join the Apple Developer Program when you’re ready to distribute or submit your apps to the App Store.