To check if your tracking is working on the lowest level on a website it is really easy. Open the website, open the dev tools, check the network tab for requests.
Doing this for apps is for more complicated.
Here are your options:
For iOS – install the Charles App https://lnkd.in/gf7m_8Xd – It works as a proxy between the app and the internet and records all outgoing request. You need to activate SSL proxing to actually see the payloads sent. And sometimes tracking vendors additionally encode the payload with Base64. Cumbersome but working
For Android – Charles Desktop App and a really complicated setup. https://lnkd.in/g7QrXCti
If you use Firebase – the debug mode is a great way to check your tracking. It needs to be enabled separately in your app: https://lnkd.in/gi_FunWe
My new way of debugging App events is using GTM server-side. Which is really great for it! I will post about it in the next days. Follow me if you are interested.