Depends on what you are testing.
If you are looking to test Google Play Game Services (ex. leaderboards) you have to upload the app to the playstore. *I made a tutorial on uploading as alpha/beta app* if you have trouble with that part.
And if you are just wanting to test your game on your device as you design for touch features and what not: Personally, I test over wifi like Kyatric explained, but I suggest you use the CocoonJS Launcher app, it will find the game like the Chrome browser will, but let you try it out in a few different environments.
You will need at least a personal license for either way mentioned.
If you don't have the license, not sure if you could just upload it to a html5 game site like Kongregate and then go to the site on your droid?
EDIT, if you go the APK route, remember that it has to be uploaded to Google Play before the Google features will work, even if plan to just install locally.