How to test Branch installs

I have a simple branch link that redirects to the stores or opens our app. This works fine but I am trying to set up a referral scheme that relies on a generated referral code appended to the branch link as a param (I don’t want to use the branch referral system as we already have a reward system built into our app)

How can I test that branch data and/or params are being passed through to our app on install?

I have universal links and associated domains turned on and my applink is specified in my app.json.
I am building to a test release channel and I have set up my branch link to point at my test build in expo.
When I click on my branch link it launches the app correctly but I’m not getting any data through.

I have tried
• branch.subscribe(bundle. {})
• branch.getLatestReferringParams()
• branch.getFirstReferringParams(true)
• branch.getFirstReferringParams()
• branch.getLatestReferringParams(true)

as well as
• Linking.addEventListener(url, {})
• Linking.getInitialURL()