Begin unit tests, relates to #35

server/cache.go

@@ -1,10 +1,17 @@
 package server
 
 import (
+	"errors"
 	_ "github.com/mattn/go-sqlite3" // SQLite driver
 	"time"
 )
 
+var (
+	errUnexpectedMessageType = errors.New("unexpected message type")
+)
+
+// cache implements a cache for messages of type "message" events,
+// i.e. message structs with the Event messageEvent.
 type cache interface {
 	AddMessage(m *message) error
 	Messages(topic string, since sinceTime) ([]*message, error)