Can I do a closed track test of a new android app and its leaderboard function before publishing the app?

As question, I tried below steps but failed.

I would like to test my android app with a leaderboard before I publish it in Google Play.

I have created a simple game and a leaderboard in Google Play Console.

I have created an android app by Android Studio and generated a signed bundle and uploaded to Google Play Console (signed by Google). I created a release for Closed tracks and released to Alpha. Clicked into 'App releases' => 'Alpha' 'Manage' => 'Manage testers' 'Closed Alpha Testing', I saw in 'Opt-in URL', the mesaage is 'An opt-in link will be available here when you publish your app.' There was no opt-in link there and I cannot proceed.

Because leaderboard is new to me and there should be several debug and fix before reaching the production quality. Many thanks.