The document proposes a solution called Marionette to enable automated testing of apps built for FirefoxOS across different Gecko environments like desktop and mobile Firefox. Marionette is a privileged WebDriver that runs in both content and privileged spaces, providing a way to control the entire device from JavaScript. It aims to support existing and future test frameworks with full device control in an easy to use way. Developers can get started by building Marionette into FirefoxOS from source code or using desktop builds of Firefox and FirefoxOS available online.