Google Play Beta testing without a published app?

You can put your Google Play Developer Console into "Advanced Mode" by clicking the button in the top right corner. Then you can activate/deactivate APKs as necessary, and upload APKs specifically for beta testers only. You do not need to change the package name.

After filling in all the details, In your developer console dont upload your APK to the production tab, only upload it in the Beta tab and click publish. Now wait for it to get published and find the playstore link which you can find after clicking the "Manage list of testers" link which is under the "Beta testers". Share this link with your beta users.

Even I made similar mistake before and then unpublished my app. Started again the publish process with different package name as Google remembers your app by the package definition. You won't be able to delete an unpublished app. That needs to be unique. When you create your app, don't upload the apk first, just prepare store listing. Once done, you will see all the panes, production, beta, alpha under APK menu. hope this helps.