replyFor method
Registers a canned result to return from the next matching
FakeChatTransport.push call with the given topic and event.
Implementation
void replyFor({
required String topic,
required String event,
required PushResult result,
}) {
_transport._replyQueue
.putIfAbsent('$topic::$event', () => <PushResult>[])
.add(result);
}