Android Auto App Testing

I have created android auto app, the issue is I am able to test it on Emulator but when I try it to test it on Head Unit my app is not listed. I have gone through different reference here , here and come to conclusion that I have to upload my app on play store for alpha and beta testing and then it is available on Head unit (HMI) but it will slow my testing and development process.

Is there any another way?

Any help will be appreciated.