tests: add missing tests for streaming chat message

src/AnthropicClient/AnthropicApiClient.cs

@@ -172,6 +172,13 @@ public class AnthropicApiClient : IAnthropicApiClient
         chatResponse is not null
       )
       {
+        var existingUsage = chatResponse.Usage;
+        var newUsage = new ChatUsage()
+        {
+          InputTokens = existingUsage.InputTokens + msgDeltaData.Usage.InputTokens,
+          OutputTokens = existingUsage.OutputTokens + msgDeltaData.Usage.OutputTokens,
+        };
+
         chatResponse = new ChatResponse()
         {
           Id = chatResponse.Id,
@@ -180,7 +187,7 @@ public class AnthropicApiClient : IAnthropicApiClient
           StopReason = msgDeltaData.Delta.StopReason,
           StopSequence = msgDeltaData.Delta.StopSequence,
           Type = chatResponse.Type,
-          Usage = msgDeltaData.Usage,
+          Usage = newUsage,
           Content = chatResponse.Content,
         };
       }

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)
   {