If you own an Android device and don't want to test your FxOS app on a real Firefox device, then a good news for a developer like you is that you can now test your FxOS apps right on your Android device. This is possible by installing the Spoof FxOS add-on to the Firefox browser of your Android device. This can be downloaded from https://addons.mozilla.org/en-US/android/addon/spoof-fxos/.
According to Mozilla, this add-on makes Firefox on Android send the Firefox OS User-Agent, and disables Flash, to make it simpler to test on Android how a site is likely to work on Firefox OS. A full emulation is not possible, especially for video and performance issues.
This means that the Firefox browser in your Android device will just pretend to be the Firefox OS browser, which enables you to test and debug your Firefox OS apps on your Android device. After downloading the add-on, enable the add-on from the browser's settings by clicking on the Enable...