Refactor unit test for server events.
Refactor unit test for server events.

JTrotta/MQTTnet,chkr1011/MQTTnet,JTrotta/MQTTnet,JTrotta/MQTTnet,JTrotta/MQTTnet,chkr1011/MQTTnet,chkr1011/MQTTnet,chkr1011/MQTTnet,chkr1011/MQTTnet