Added unit tests for #2864
Added unit tests for #2864

kaybutter/AFNetworking,michal-olszewski/AFNetworking-CustomCallbacks,jeremiahyan/AFNetworking,dilumn/AFNetworking,BohemianCoding/AFNetworking,OmarPedraza/AFNetworking,dake/AFNetworking,easyui/AFNetworking,wangxiaoxiang/AFNetworking,NextThought/AFNetworking,michal-olszewski/AFNetworking-CustomCallbacks,donholly/AFNetworking,kevin-zqw/AFNetworking,kiurentu/AFNetworking,kiurentu/AFNetworking