In order to send a test to several devices, you may have to create a Custom Audience with all your test devices, and target it on a campaign.
1- To create a new custom audience, go to Settings > Audiences > and click on "Upload an Audience".
2- Upload a .txt, or .csv file, with one identifier per line only. It can be Custom User IDS or IDFA (iOS) / Custom User IDs or Advertising IDs GAID (Android).
3- When your custom audience is uploaded, create your campaign and target your custom audience. Finally, click on "Save & Run" to send your push.
💡 Your estimated reach can be 0 tokens, since there is only a few people on your custom audience compared to your userbase: