AppBuilder offers out-of-the-box a large selection of simulation options.
AppBuilder includes a full-featured simulator available via the CLI or in-browser with which you can view how your app looks and behaves in many device sizes and types.
Alternately, test your app using native emulators associated with Android, Windows Phone, and Xcode.
Test in an app
AppBuilder also offers the Companion App, a way for you to test your app on a device without provisioning, which eases iOS development in particular.
Test in a browser
There are several ways to test an app's behavior.
By typing 'phonegap emulate ios' in the command line you can see how your app looks on an iOS simulator, and similarly for Android emulators. Simulators are provided by native platforms by downloading Android tools or Xcode.
Test on a device
PhoneGap Build offers a way to download builds for testing on a device, but you do need to include provisioning profiles for your iOS testers.
Test using an app and browser
The PhoneGap App allows wireless emulation between your local app and its installation on device. You can enter a url and use Chrome's developer tools to debug. This emulation requires the Chrome browser and the Ripple emulation extension to be installed. Alternately, you can use Chrome's Dev Tools with the Device Emulation extension installed. For on-device debugging you can make use of Safari's Developer Tools to debug remote code for iOS apps. For other devices, you can also use Weinre to get an idea of bugs that occur on a device. Finally, you can always use native development tools such as Xcode's console and Android's 'adb' toolset to debug.