I tried Christos' test case for the challenge, on my "WWW-Authenticate" branch, using this "unit test":
https://gist.github.com/cvasilak/3f64c3c806b0af11fef6

Works perfect and I am noticing the expected flow:

The server receives REQ, returns 401
our iOS client library is reacting on the challenge and sends the request with the proper credentials.
Push Server accepts "proper" request, and delivers Push Notification to the cloud (here APNs)
got a Push Message to my device with this.

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