InstanceHeartbeats: []InstanceHeartbeat{ InstanceHeartbeat{ CCPartition: "default", AppGuid: "abc", AppVersion: "123", InstanceGuid: "xyz", InstanceIndex: 1, State: InstanceStateRunning, StateTimestamp: 1377816348.0, }, }, } message := make(chan []byte, 0) fakeMessageBus.Subscribe("dea.heartbeat", func(payload []byte) { message <- payload }) publisher.PublishHeartbeat(heartbeat) var parsedJson map[string]interface{} err := json.Unmarshal(<-message, &parsedJson) Ω(err).ShouldNot(HaveOccured()) Ω(parsedJson["dea"]).Should(Equal("ABC")) droplets := parsedJson["droplets"].([]interface{}) Ω(droplets).Should(HaveLen(1)) instanceHeartbeat := droplets[0].(map[string]interface{}) Ω(instanceHeartbeat["cc_partition"]).Should(Equal("default"))