Developing applications for multiple devices requires consistent device-specific testing. The iOS simulator included in the iOS SDK provides simulation for all Apple devices. With Xcode 5, selecting the proper device to build for has also been streamlined into a single drop-down option found on the toolbar.
Clicking on the name of the current device on the left of the toolbar will provide a drop-down menu. Any and all physical devices connected to your computer will appear on the top of the list (you may have to scroll up to see them), and all standard iOS simulator devices will appear below.
Simply select the device you wish to test for, and click on Run. The simulator will launch and switch to the selected device. The following screenshot lists the devices in the drop-down menu: