firebase/reactfire — pull request #24 by insin (2014-10-23 12:59:03+00:00)
Title: Allow a callback to be passed for the cancelCallback argument to firebaseRef.on()

Adds API suggested in #19

Not sure how to add a test to your suite for this, but have checked it at least works locally in react-hn against the Hacker News API, which errors when attempting to load delayed comments