Enhance export test

Hcs.Broker/MessageCapturer/FileMessageCapturer.cs

@@ -12,6 +12,10 @@ namespace Hcs.Broker.MessageCapturer
         private readonly string directory = directory;
         private readonly ILogger logger = logger;
 
+        public string LastFileName { get; private set; }
+
+        public event Action<string> OnFileWritten;
+
         public void CaptureMessage(bool sent, string messageBody)
         {
             var index = 0;
@@ -43,6 +47,10 @@ namespace Hcs.Broker.MessageCapturer
             logger?.WriteLine($"Capturing message to file {fileName}...");
 
             File.WriteAllText(fileName, messageBody, Encoding.UTF8);
+
+            LastFileName = fileName;
+
+            OnFileWritten?.Invoke(fileName);
         }
     }
 }