Apart from the aforementioned ways of testing an app, we can build automated test cases using frameworks such as Appium (http://appium.io/). This way, using the Device Farm, we can upload the APK or IPA followed by the automation test suite. Then we pick a group of devices and execute the tests on them.
You can look up Automating hybrid apps (http://appium.io/slate/en/master/?ruby#automating-hybrid-apps) and Verifying a Cordova or PhoneGap build with Smoke Tests and Appium (http://ezosaleh.com/verifying-a-cordovaphonegap-build-with-smoke-tests-appium) to get an idea on writing automated tests for your hybrid app.
You can run these automated tests locally too in an emulator if you choose to.
