Several years ago I had a conversation with a cool guy working at Opera, Charles McCathieNevile. He told me in mixed English/Italian, "Mobile is tutto casino!" (Mobile is total chaos). This was true in 2004 and it's still just as true today due to the high device fragmentation and difference in screen resolutions.

In order to emulate devices you can use several tools including the ones provided by the major SDK vendors. Usually these tools are time-consuming and sometimes not easy to configure; for this reason, I strongly encourage you to use the web as your development and debugging platform.

One of the greatest advantages to using PhoneGap is that you can use web standards and thus avoid having to continuously test the app in the browser emulator that comes with the SDK of each mobile platform. It doesn't mean that you don't need to emulate the app at all or that you don't have to test it in a real device, but you can safely assume that it's enough to test the UI and the main user interactions inside your desktop browser.

There is a very interesting open source project called Ripple that lets you emulate several mobile platforms in your browser. Unfortunately, at the time of writing, it's available only for Chrome. You can get the Ripple extension for Chrome at https://chrome.google.com/webstore/detail/ripple-emulator-beta/geelfhphabnejjhdalkjhgipohgpdnoc; after you install the extension, you can access it from the top right of your Chrome installation.

By clicking on the Ripple icon, the extension starts to emulate one of the available platforms, including Mobile Web, PhoneGap, and Blackberry 10 Web Works. The Mobile Web platform offers several devices to emulate with skins and different orientations.

When selecting the PhoneGap platform, you can emulate the device and test in a familiar browser environment the app features and interactions with the Apache Cordova framework.

All the relevant device information and settings are available in the same window you can use to debug your app.

On the left side you can select the device, its orientation, get detailed information about the device, and simulate the accelerometer. On the right side it's possible to set up the network settings, the lag, the geo location information, and play with events. You can select the event you want to emulate and then fire it; in this way you can easily simulate device-specific events such as the pressure of the back button or of the home button. If you have an appropriate XML configuration file in the app folder, you can get a graphical representation of it inside Ripple.