The final stages of an avionics installation can be the most critical because thats when the configuration and final testing occur. Unfortunately, its when a shop can be rushed to the point where you-the aircraft owner-are left holding the bag to test newly installed gear, which includes critical ADS-B equipment. The good news: Shops that do the most ADS-B retrofits will own the specialized test gear to make sure the system is programmed and properly tested before you fly the aircraft away. The better shops will fly it with you for a final check. But for shops that are less equipped, you’ll have to fly it off yourself and eyeball the data on the Public ADS-B Performance Report, or PAPR. Link to this automated tool at https://tinyurl.com/y9hrtsyw. It can tell a shop a lot about the systems performance should they have to troubleshoot it. When the government was paying out rebate checks for ADS-B upgrades, it required specific flight testing and a validation report for conformity. Thats no longer the case, but you might follow similar guidance when validating a new install. The FAAs advisory circular 20-165B provides guidance for ADS-B Out system installations and airworthiness approvals. In it you’ll find the recommended flight profiles and maneuvers to perform on the flight test. Worth mentioning is that a typical FAR 91.413 transponder test wont check a 1090ES transponders ADS-B data output.