tests: add missing tests for streaming chat message

src/AnthropicClient/Models/EventData.cs

@@ -1,5 +1,3 @@
-using System.Text.Json.Serialization;
-
 namespace AnthropicClient.Models;
 
 public abstract class EventData

src/AnthropicClient/Models/MessageCompleteEventData.cs

@@ -1,11 +1,9 @@
-using System.Text.Json.Serialization;
-
 namespace AnthropicClient.Models;
 
 public class MessageCompleteEventData : EventData
 {
-  public AnthropicHeaders Headers { get; init; } = new();
-  public ChatResponse Message { get; init; } = new();
+  public AnthropicHeaders Headers { get; init; }
+  public ChatResponse Message { get; init; }
 
   public MessageCompleteEventData(ChatResponse message, AnthropicHeaders headers) : base(EventType.MessageComplete)
   {