Rob from Twilio is here.
The big question here is about using Twilio test credentials when creating against SMS API. You are right - StatusCallbacks do not start for the Messages resource when called with test credentials. In the documentation section of the StatusCallback link, you indicate that the API response will return the value that you set for the StatusCallback parameter when testing the purchase of a phone number without creating a message or phone call.
I am testing StatusCallbacks by mocking the StatusCallback request in my test using the parameters in the documentation here . The corresponding parameter that you want to test in the new message resource, MessageStatus .
source share