add the started_at as well and then work out the duration when requested

lib/travis/notification/instrument.rb

@@ -41,16 +41,20 @@ def publish(message, status, args, method)
         async :publish, :queue => :instrumentation
       end
 
-      attr_reader :config, :target, :result, :exception, :finished_at, :message, :status
+      attr_reader :config, :target, :result, :exception, :started_at, :finished_at, :message, :status
 
       def initialize(message, status, payload)
         @target, @result, @exception = payload.values_at(:target, :result, :exception)
-        @finished_at = payload[:finished_at]
+        @started_at, @finished_at = payload.values_at(:started_at, :finished_at)
         @config = { :message => message }
         @config[:exception] = exception if exception
         @status = status.to_sym
       end
 
+      def duration
+        @duration ||= (finished_at ? finished_at - started_at : nil)
+      end
+
       private
 
         def publish(event = {})