diff --git a/src/AnthropicClient/AnthropicApiClient.cs b/src/AnthropicClient/AnthropicApiClient.cs
index 5307760..5046929 100644
--- a/src/AnthropicClient/AnthropicApiClient.cs
+++ b/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,
         };
       }
diff --git a/src/AnthropicClient/Models/EventData.cs b/src/AnthropicClient/Models/EventData.cs
index e73d531..d40914a 100644
--- a/src/AnthropicClient/Models/EventData.cs
+++ b/src/AnthropicClient/Models/EventData.cs
@@ -1,5 +1,3 @@
-using System.Text.Json.Serialization;
-
 namespace AnthropicClient.Models;
 
 public abstract class EventData
diff --git a/src/AnthropicClient/Models/MessageCompleteEventData.cs b/src/AnthropicClient/Models/MessageCompleteEventData.cs
index 85218ad..bdd62df 100644
--- a/src/AnthropicClient/Models/MessageCompleteEventData.cs
+++ b/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)
   {
diff --git a/tests/AnthropicClient.Tests/Unit/Models/AnthropicEventTests.cs b/tests/AnthropicClient.Tests/Unit/Models/AnthropicEventTests.cs
new file mode 100644
index 0000000..931616b
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/AnthropicEventTests.cs
@@ -0,0 +1,372 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class AnthropicEventTests : SerializationTest
+{
+  private readonly string _testMessageStartJson = @"{
+    ""type"": ""message_start"",
+    ""data"": {
+      ""message"": {
+        ""id"": ""msg_014p7gG3wDgGV9EUtLvnow3U"",
+        ""type"": ""message"",
+        ""role"": ""assistant"",
+        ""model"": ""claude-3-haiku-20240307"",
+        ""stop_sequence"": """",
+        ""usage"": {
+          ""input_tokens"": 472,
+          ""output_tokens"": 2
+        },
+        ""content"": [],
+        ""stop_reason"": """"
+      },
+      ""type"": ""message_start""
+    }
+  }";
+
+  private readonly string _testContentBlockStartJson = @"{
+    ""type"": ""content_block_start"",
+    ""data"": {
+      ""index"": 0,
+      ""content_block"": {
+        ""type"": ""text"",
+        ""text"": ""Okay""
+      },
+      ""type"": ""content_block_start""
+    }
+  }";
+
+  private readonly string _testPingJson = @"{
+    ""type"": ""ping"",
+    ""data"": {
+      ""type"": ""ping""
+    }
+  }";
+
+  private readonly string _testContentBlockDeltaJson = @"{
+    ""type"": ""content_block_delta"",
+    ""data"": {
+      ""index"": 0,
+      ""delta"": {
+        ""type"": ""text_delta"",
+        ""text"": ""Okay""
+      },
+      ""type"": ""content_block_delta""
+    }
+  }";
+
+  private readonly string _testContentBlockStopJson = @"{
+    ""type"": ""content_block_stop"",
+    ""data"": {
+      ""index"": 0,
+      ""type"": ""content_block_stop""
+    }
+  }";
+
+  private readonly string _testMessageDeltaJson = @"{
+    ""type"": ""message_delta"",
+    ""data"": {
+      ""delta"": {
+        ""stop_reason"": ""tool_use"",
+        ""stop_sequence"": """"
+      },
+      ""usage"": {
+        ""output_tokens"": 89,
+        ""input_tokens"": 0
+      },
+      ""type"": ""message_delta""
+    }
+  }";
+
+  private readonly string _testMessageStopJson = @"{
+    ""type"": ""message_stop"",
+    ""data"": {
+      ""type"": ""message_stop""
+    }
+  }";
+
+  private readonly string _testErrorJson = @"{
+    ""type"": ""error"",
+    ""data"": {
+      ""error"": {
+        ""type"": ""api_error"",
+        ""message"": ""An error occurred.""
+      },
+      ""type"": ""error""
+    }
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var expectedType = EventType.MessageStart;
+    var expected = new MessageStartEventData
+    {
+      Type = EventType.MessageStart,
+      Message = new()
+    };
+
+    var actual = new AnthropicEvent(expectedType, expected);
+
+    actual.Type.Should().Be(expectedType);
+    actual.Data.Should().BeSameAs(expected);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var eventData = new MessageStartEventData
+    {
+      Type = EventType.MessageStart,
+      Message = new()
+      {
+        Id = "msg_014p7gG3wDgGV9EUtLvnow3U",
+        Type = "message",
+        Role = "assistant",
+        Model = "claude-3-haiku-20240307",
+        StopSequence = string.Empty,
+        Usage = new()
+        {
+          InputTokens = 472,
+          OutputTokens = 2
+        },
+        Content = [],
+        StopReason = string.Empty
+      }
+    };
+
+    var e = new AnthropicEvent(EventType.MessageStart, eventData);
+
+    var actual = Serialize(e);
+
+    JsonAssert.Equal(_testMessageStartJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenMessageStartEventDeserialized_ItShouldHaveBeExpectedType()
+  {
+    var expected = new MessageStartEventData
+    {
+      Type = EventType.MessageStart,
+      Message = new()
+      {
+        Id = "msg_014p7gG3wDgGV9EUtLvnow3U",
+        Type = "message",
+        Role = "assistant",
+        Model = "claude-3-haiku-20240307",
+        StopSequence = string.Empty,
+        Usage = new()
+        {
+          InputTokens = 472,
+          OutputTokens = 2
+        },
+        Content = [],
+        StopReason = string.Empty
+      }
+    };
+
+    var actual = Deserialize<AnthropicEvent>(_testMessageStartJson);
+
+    actual!.Type.Should().Be(expected.Type);
+    actual.Data.Should().BeEquivalentTo(expected);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenContentBlockStartEventSerialized_ItShouldHaveExpectedShape()
+  {
+    var eventData = new ContentStartEventData(0, new TextContent("Okay"));
+
+    var e = new AnthropicEvent(EventType.ContentBlockStart, eventData);
+
+    var actual = Serialize(e);
+
+    JsonAssert.Equal(_testContentBlockStartJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenContentBlockStartEventDeserialized_ItShouldHaveExpectedType()
+  {
+    var expected = new ContentStartEventData(0, new TextContent("Okay"));
+
+    var actual = Deserialize<AnthropicEvent>(_testContentBlockStartJson);
+
+    actual!.Type.Should().Be(expected.Type);
+    actual.Data.Should().BeEquivalentTo(expected);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenPingEventSerialized_ItShouldHaveExpectedShape()
+  {
+    var eventData = new PingEventData();
+
+    var e = new AnthropicEvent(EventType.Ping, eventData);
+
+    var actual = Serialize(e);
+
+    JsonAssert.Equal(_testPingJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenPingEventDeserialized_ItShouldHaveExpectedType()
+  {
+    var expected = new PingEventData();
+
+    var actual = Deserialize<AnthropicEvent>(_testPingJson);
+
+    actual!.Type.Should().Be(expected.Type);
+    actual.Data.Should().BeEquivalentTo(expected);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenContentBlockDeltaEventSerialized_ItShouldHaveExpectedShape()
+  {
+    var eventData = new ContentDeltaEventData(0, new TextDelta("Okay"));
+
+    var e = new AnthropicEvent(EventType.ContentBlockDelta, eventData);
+
+    var actual = Serialize(e);
+
+    JsonAssert.Equal(_testContentBlockDeltaJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenContentBlockDeltaEventDeserialized_ItShouldHaveExpectedType()
+  {
+    var expected = new ContentDeltaEventData(0, new TextDelta("Okay"));
+
+    var actual = Deserialize<AnthropicEvent>(_testContentBlockDeltaJson);
+
+    actual!.Type.Should().Be(expected.Type);
+    actual.Data.Should().BeEquivalentTo(expected);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenContentBlockStopEventSerialized_ItShouldHaveExpectedShape()
+  {
+    var eventData = new ContentStopEventData(0);
+
+    var e = new AnthropicEvent(EventType.ContentBlockStop, eventData);
+
+    var actual = Serialize(e);
+
+    JsonAssert.Equal(_testContentBlockStopJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenContentBlockStopEventDeserialized_ItShouldHaveExpectedType()
+  {
+    var expected = new ContentStopEventData(0);
+
+    var actual = Deserialize<AnthropicEvent>(_testContentBlockStopJson);
+
+    actual!.Type.Should().Be(expected.Type);
+    actual.Data.Should().BeEquivalentTo(expected);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenMessageDeltaEventSerialized_ItShouldHaveExpectedShape()
+  {
+    var eventData = new MessageDeltaEventData
+    {
+      Type = EventType.MessageDelta,
+      Delta = new()
+      {
+        StopReason = "tool_use",
+        StopSequence = string.Empty,
+      },
+      Usage = new()
+      {
+        OutputTokens = 89,
+      }
+    };
+
+    var e = new AnthropicEvent(EventType.MessageDelta, eventData);
+
+    var actual = Serialize(e);
+
+    JsonAssert.Equal(_testMessageDeltaJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenMessageDeltaEventDeserialized_ItShouldHaveExpectedType()
+  {
+    var expected = new MessageDeltaEventData
+    {
+      Type = EventType.MessageDelta,
+      Delta = new()
+      {
+        StopReason = "tool_use",
+        StopSequence = string.Empty,
+      },
+      Usage = new()
+      {
+        OutputTokens = 89,
+        InputTokens = 0
+      }
+    };
+
+    var actual = Deserialize<AnthropicEvent>(_testMessageDeltaJson);
+
+    actual!.Type.Should().Be(expected.Type);
+    actual.Data.Should().BeEquivalentTo(expected);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenMessageStopEventSerialized_ItShouldHaveExpectedShape()
+  {
+    var eventData = new MessageStopEventData();
+
+    var e = new AnthropicEvent(EventType.MessageStop, eventData);
+
+    var actual = Serialize(e);
+
+    JsonAssert.Equal(_testMessageStopJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenMessageStopEventDeserialized_ItShouldHaveExpectedType()
+  {
+    var expected = new MessageStopEventData();
+
+    var actual = Deserialize<AnthropicEvent>(_testMessageStopJson);
+
+    actual!.Type.Should().Be(expected.Type);
+    actual.Data.Should().BeEquivalentTo(expected);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenErrorEventSerialized_ItShouldHaveExpectedShape()
+  {
+    var eventData = new ErrorEventData(new ApiError("An error occurred."));
+
+    var e = new AnthropicEvent(EventType.Error, eventData);
+
+    var actual = Serialize(e);
+
+    JsonAssert.Equal(_testErrorJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenErrorEventDeserialized_ItShouldHaveExpectedType()
+  {
+    var expected = new ErrorEventData(new ApiError("An error occurred."));
+
+    var actual = Deserialize<AnthropicEvent>(_testErrorJson);
+
+    actual!.Type.Should().Be(expected.Type);
+    actual.Data.Should().BeEquivalentTo(expected);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenTypeUnknown_ItShouldThrow()
+  {
+    var json = @"{
+      ""type"": ""unknown"",
+      ""data"": {
+        ""type"": ""unknown""
+      }
+    }";
+
+    Action act = () => Deserialize<AnthropicEvent>(json);
+
+    act.Should().Throw<JsonException>();
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/ContentDeltaEventDataTests.cs b/tests/AnthropicClient.Tests/Unit/Models/ContentDeltaEventDataTests.cs
new file mode 100644
index 0000000..1f226c1
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/ContentDeltaEventDataTests.cs
@@ -0,0 +1,103 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class ContentDeltaEventDataTests : SerializationTest
+{
+  private readonly string _testJsonWithTextDelta = @"{
+    ""type"": ""content_block_delta"",
+    ""index"": 0,
+    ""delta"": {
+      ""type"": ""text_delta"",
+      ""text"": ""Hello World!""
+    }
+  }";
+
+  private readonly string _testJsonWithInputDelta = @"{
+    ""type"": ""content_block_delta"",
+    ""index"": 0,
+    ""delta"": {
+      ""type"": ""input_json_delta"",
+      ""partial_json"": ""Hello""
+    }
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var index = 0;
+    var text = "Hello World!";
+    var textDelta = new TextDelta(text);
+    var contentDeltaEventData = new ContentDeltaEventData(index, textDelta);
+
+    contentDeltaEventData.Type.Should().Be("content_block_delta");
+    contentDeltaEventData.Delta.Should().BeSameAs(textDelta);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerializedWithTextDelta_ItShouldHaveExpectedShape()
+  {
+    var index = 0;
+    var text = "Hello World!";
+    var textDelta = new TextDelta(text);
+    var contentDeltaEventData = new ContentDeltaEventData(index, textDelta);
+
+    var actual = Serialize(contentDeltaEventData);
+
+    JsonAssert.Equal(_testJsonWithTextDelta, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserializedWithTextDelta_ItShouldHaveExpectedProperties()
+  {
+    var index = 0;
+    var text = "Hello World!";
+    var textDelta = new TextDelta(text);
+    var contentDeltaEventData = new ContentDeltaEventData(index, textDelta);
+
+    var actual = Deserialize<ContentDeltaEventData>(_testJsonWithTextDelta);
+
+    actual.Should().BeEquivalentTo(contentDeltaEventData);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerializedWithInputDelta_ItShouldHaveExpectedShape()
+  {
+    var index = 0;
+    var input = "Hello";
+    var inputDelta = new JsonDelta(input);
+    var contentDeltaEventData = new ContentDeltaEventData(index, inputDelta);
+
+    var actual = Serialize(contentDeltaEventData);
+
+    JsonAssert.Equal(_testJsonWithInputDelta, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserializedWithInputDelta_ItShouldHaveExpectedProperties()
+  {
+    var index = 0;
+    var input = "Hello";
+    var inputDelta = new JsonDelta(input);
+    var contentDeltaEventData = new ContentDeltaEventData(index, inputDelta);
+
+    var actual = Deserialize<ContentDeltaEventData>(_testJsonWithInputDelta);
+
+    actual.Should().BeEquivalentTo(contentDeltaEventData);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserializedWithUnknownDeltaType_ItShouldThrowJsonException()
+  {
+    var json = @"{
+      ""type"": ""content_block_delta"",
+      ""index"": 0,
+      ""delta"": {
+        ""type"": ""unknown_delta"",
+        ""text"": ""Hello World!""
+      }
+    }";
+
+    var action = () => Deserialize<ContentDeltaEventData>(json);
+
+    action.Should().Throw<JsonException>();
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/ContentDeltaTypeTests.cs b/tests/AnthropicClient.Tests/Unit/Models/ContentDeltaTypeTests.cs
new file mode 100644
index 0000000..9bddaa2
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/ContentDeltaTypeTests.cs
@@ -0,0 +1,24 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class ContentDeltaTypeTests
+{
+  [Fact]
+  public void TextDelta_WhenCalled_ItShouldReturnExpectedValue()
+  {
+    var expected = "text_delta";
+    
+    var actual = ContentDeltaType.TextDelta;
+    
+    actual.Should().Be(expected);
+  }
+
+  [Fact]
+  public void JsonDelta_WhenCalled_ItShouldReturnExpectedValue()
+  {
+    var expected = "input_json_delta";
+    
+    var actual = ContentDeltaType.JsonDelta;
+    
+    actual.Should().Be(expected);
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/ContentStartEventDataTests.cs b/tests/AnthropicClient.Tests/Unit/Models/ContentStartEventDataTests.cs
new file mode 100644
index 0000000..25bf30e
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/ContentStartEventDataTests.cs
@@ -0,0 +1,77 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class ContentStartEventDataTests : SerializationTest
+{
+  private readonly string _testJsonWithTextBlock = @"{
+    ""type"": ""content_block_start"",
+    ""index"": 0,
+    ""content_block"": {
+      ""type"": ""text"",
+      ""text"": ""Hello World!""
+    }
+  }";
+
+  private readonly string _testJsonWithToolUseBlock = @"{
+    ""type"": ""content_block_start"",
+    ""index"": 0,
+    ""content_block"": {
+      ""type"": ""tool_use"",
+      ""id"": ""toolu_01T1x1fJ34qAmk2tNTrN7Up6"",
+      ""name"": ""get_weather"",
+      ""input"": {}}
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var index = 0;
+    var textContent = new TextContent("Hello World!");
+    var contentStartEventData = new ContentStartEventData(index, textContent);
+
+    contentStartEventData.Type.Should().Be("content_block_start");
+    contentStartEventData.Index.Should().Be(index);
+    contentStartEventData.ContentBlock.Should().BeSameAs(textContent);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerializedWithTextContent_ItShouldHaveExpectedShape()
+  {
+    var index = 0;
+    var textContent = new TextContent("Hello World!");
+    var contentStartEventData = new ContentStartEventData(index, textContent);
+
+    var actual = Serialize(contentStartEventData);
+
+    JsonAssert.Equal(_testJsonWithTextBlock, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserializedWithTextContent_ItShouldHaveExpectedProperties()
+  {
+    var index = 0;
+    var textContent = new TextContent("Hello World!");
+    var contentStartEventData = new ContentStartEventData(index, textContent);
+
+    var actual = Deserialize<ContentStartEventData>(_testJsonWithTextBlock);
+
+    actual.Should().BeEquivalentTo(contentStartEventData);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerializedWithToolUseContent_ItShouldHaveExpectedShape()
+  {
+    var index = 0;
+    var toolUseContent = new ToolUseContent()
+    {
+      Id = "toolu_01T1x1fJ34qAmk2tNTrN7Up6",
+      Name = "get_weather",
+      Input = []
+    };
+  
+    var contentStartEventData = new ContentStartEventData(index, toolUseContent);
+
+    var actual = Serialize(contentStartEventData);
+
+    JsonAssert.Equal(_testJsonWithToolUseBlock, actual);
+  }
+}
diff --git a/tests/AnthropicClient.Tests/Unit/Models/ContentStopEventDataTests.cs b/tests/AnthropicClient.Tests/Unit/Models/ContentStopEventDataTests.cs
new file mode 100644
index 0000000..03155e6
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/ContentStopEventDataTests.cs
@@ -0,0 +1,41 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class ContentStopEventDataTests : SerializationTest
+{
+  private readonly string _testJson = @"{
+    ""type"": ""content_block_stop"",
+    ""index"": 0
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var index = 0;
+    var contentStopEventData = new ContentStopEventData(index);
+
+    contentStopEventData.Type.Should().Be("content_block_stop");
+    contentStopEventData.Index.Should().Be(index);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var index = 0;
+    var contentStopEventData = new ContentStopEventData(index);
+
+    var actual = Serialize(contentStopEventData);
+
+    JsonAssert.Equal(_testJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedProperties()
+  {
+    var index = 0;
+    var contentStopEventData = new ContentStopEventData(index);
+
+    var actual = Deserialize<ContentStopEventData>(_testJson);
+
+    actual.Should().BeEquivalentTo(contentStopEventData);
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/ErrorEventDataTests.cs b/tests/AnthropicClient.Tests/Unit/Models/ErrorEventDataTests.cs
new file mode 100644
index 0000000..b88d83d
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/ErrorEventDataTests.cs
@@ -0,0 +1,44 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class ErrorEventDataTests : SerializationTest
+{
+  private readonly string _testJson = @"{
+    ""type"": ""error"",
+    ""error"": {
+      ""type"": ""api_error"",
+      ""message"": ""An error occurred.""
+    }
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var error = new ApiError("An error occurred.");
+    var errorEventData = new ErrorEventData(error);
+
+    errorEventData.Type.Should().Be("error");
+    errorEventData.Error.Should().BeSameAs(error);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var error = new ApiError("An error occurred.");
+    var errorEventData = new ErrorEventData(error);
+
+    var actual = Serialize(errorEventData);
+
+    JsonAssert.Equal(_testJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedProperties()
+  {
+    var error = new ApiError("An error occurred.");
+    var errorEventData = new ErrorEventData(error);
+
+    var actual = Deserialize<ErrorEventData>(_testJson);
+
+    actual.Should().BeEquivalentTo(errorEventData);
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/JsonDeltaTests.cs b/tests/AnthropicClient.Tests/Unit/Models/JsonDeltaTests.cs
new file mode 100644
index 0000000..c153425
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/JsonDeltaTests.cs
@@ -0,0 +1,40 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class JsonDeltaTests : SerializationTest
+{
+  private readonly string _testJson = @"{
+    ""type"": ""input_json_delta"",
+    ""partial_json"": ""{\""key\"": \""value\""}""
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var partialJson = "{\"key\": \"value\"}";
+
+    var jsonDelta = new JsonDelta(partialJson);
+
+    jsonDelta.Type.Should().Be("input_json_delta");
+    jsonDelta.PartialJson.Should().Be(partialJson);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var jsonDelta = new JsonDelta("{\"key\": \"value\"}");
+
+    var actual = Serialize(jsonDelta);
+
+    JsonAssert.Equal(_testJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedProperties()
+  {
+    var expected = new JsonDelta("{\"key\": \"value\"}");
+
+    var actual = Deserialize<JsonDelta>(_testJson);
+
+    actual.Should().BeEquivalentTo(expected);
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/MessageCompleteEventDataTests.cs b/tests/AnthropicClient.Tests/Unit/Models/MessageCompleteEventDataTests.cs
new file mode 100644
index 0000000..8b456d7
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/MessageCompleteEventDataTests.cs
@@ -0,0 +1,16 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class MessageCompleteEventDataTests
+{
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var expectedMessage = new ChatResponse();
+    var expectedHeaders = new AnthropicHeaders();
+
+    var messageCompleteEventData = new MessageCompleteEventData(expectedMessage, expectedHeaders);
+
+    messageCompleteEventData.Message.Should().BeSameAs(expectedMessage);
+    messageCompleteEventData.Headers.Should().BeSameAs(expectedHeaders);
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/MessageDeltaEventDataTests.cs b/tests/AnthropicClient.Tests/Unit/Models/MessageDeltaEventDataTests.cs
new file mode 100644
index 0000000..b514fbd
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/MessageDeltaEventDataTests.cs
@@ -0,0 +1,53 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class MessageDeltaEventDataTests : SerializationTest
+{
+  private readonly string _testJson = @"{
+    ""type"": ""message_delta"",
+    ""delta"": {
+      ""stop_reason"": ""max_tokens"",
+      ""stop_sequence"": ""max_tokens""
+    },
+    ""usage"": {
+      ""input_tokens"": 1,
+      ""output_tokens"": 1
+    }
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var expectedDelta = new MessageDelta("max_tokens", "max_tokens");
+    var expectedUsage = new ChatUsage { InputTokens = 1, OutputTokens = 1 };
+
+    var messageDeltaEventData = new MessageDeltaEventData(expectedDelta, expectedUsage);
+
+    messageDeltaEventData.Delta.Should().BeSameAs(expectedDelta);
+    messageDeltaEventData.Usage.Should().BeSameAs(expectedUsage);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var expectedDelta = new MessageDelta("max_tokens", "max_tokens");
+    var expectedUsage = new ChatUsage { InputTokens = 1, OutputTokens = 1 };
+
+    var messageDeltaEventData = new MessageDeltaEventData(expectedDelta, expectedUsage);
+
+    var actualJson = Serialize(messageDeltaEventData);
+
+    JsonAssert.Equal(_testJson, actualJson);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedValues()
+  {
+    var expectedDelta = new MessageDelta("max_tokens", "max_tokens");
+    var expectedUsage = new ChatUsage { InputTokens = 1, OutputTokens = 1 };
+
+    var messageDeltaEventData = Deserialize<MessageDeltaEventData>(_testJson);
+
+    messageDeltaEventData!.Delta.Should().BeEquivalentTo(expectedDelta);
+    messageDeltaEventData.Usage.Should().BeEquivalentTo(expectedUsage);
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/MessageDeltaTests.cs b/tests/AnthropicClient.Tests/Unit/Models/MessageDeltaTests.cs
new file mode 100644
index 0000000..db8b52b
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/MessageDeltaTests.cs
@@ -0,0 +1,43 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class MessageDeltaTests : SerializationTest
+{
+  private readonly string _testJson = @"{
+    ""stop_reason"": ""max_tokens"",
+    ""stop_sequence"": ""max_tokens""
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var expectedStopReason = "max_tokens";
+    var expectedStopSequence = "max_tokens";
+
+    var messageDelta = new MessageDelta(expectedStopReason, expectedStopSequence);
+
+    messageDelta.StopReason.Should().Be(expectedStopReason);
+    messageDelta.StopSequence.Should().Be(expectedStopSequence);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var messageDelta = new MessageDelta("max_tokens", "max_tokens");
+
+    var actualJson = Serialize(messageDelta);
+
+    JsonAssert.Equal(_testJson, actualJson);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedProperties()
+  {
+    var expectedStopReason = "max_tokens";
+    var expectedStopSequence = "max_tokens";
+
+    var messageDelta = Deserialize<MessageDelta>(_testJson);
+
+    messageDelta!.StopReason.Should().Be(expectedStopReason);
+    messageDelta.StopSequence.Should().Be(expectedStopSequence);
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/MessageStartEventDataTests.cs b/tests/AnthropicClient.Tests/Unit/Models/MessageStartEventDataTests.cs
new file mode 100644
index 0000000..2df48d1
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/MessageStartEventDataTests.cs
@@ -0,0 +1,83 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class MessageStartEventDataTests : SerializationTest
+{
+  private readonly string _testJson = @"{
+    ""type"": ""message_start"",
+    ""message"": {
+      ""id"": ""msg_1nZdL29xx5MUA1yADyHTEsnR8uuvGzszyY"",
+      ""type"": ""message"",
+      ""role"": ""assistant"",
+      ""content"": [],
+      ""model"": ""claude-3-5-sonnet-20240620"",
+      ""stop_reason"": """",
+      ""stop_sequence"": """",
+      ""usage"": {
+        ""input_tokens"": 25,
+        ""output_tokens"": 1
+      }
+    }
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var expectedMessage = new ChatResponse
+    {
+      Id = "msg_1nZdL29xx5MUA1yADyHTEsnR8uuvGzszyY",
+      Type = "message",
+      Role = "assistant",
+      Content = [],
+      Model = "claude-3-5-sonnet-20240620",
+      StopReason = string.Empty,
+      StopSequence = string.Empty,
+      Usage = new ChatUsage { InputTokens = 25, OutputTokens = 1 }
+    };
+
+    var messageStartEventData = new MessageStartEventData(expectedMessage);
+
+    messageStartEventData.Message.Should().BeSameAs(expectedMessage);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var expectedMessage = new ChatResponse
+    {
+      Id = "msg_1nZdL29xx5MUA1yADyHTEsnR8uuvGzszyY",
+      Type = "message",
+      Role = "assistant",
+      Content = [],
+      Model = "claude-3-5-sonnet-20240620",
+      StopReason = string.Empty,
+      StopSequence = string.Empty,
+      Usage = new ChatUsage { InputTokens = 25, OutputTokens = 1 }
+    };
+
+    var messageStartEventData = new MessageStartEventData(expectedMessage);
+
+    var actualJson = Serialize(messageStartEventData);
+
+    JsonAssert.Equal(_testJson, actualJson);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedValues()
+  {
+    var expectedMessage = new ChatResponse
+    {
+      Id = "msg_1nZdL29xx5MUA1yADyHTEsnR8uuvGzszyY",
+      Type = "message",
+      Role = "assistant",
+      Content = [],
+      Model = "claude-3-5-sonnet-20240620",
+      StopReason = string.Empty,
+      StopSequence = string.Empty,
+      Usage = new ChatUsage { InputTokens = 25, OutputTokens = 1 }
+    };
+
+    var messageStartEventData = Deserialize<MessageStartEventData>(_testJson);
+
+    messageStartEventData!.Message.Should().BeEquivalentTo(expectedMessage);
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/StreamChatMessageRequestTests.cs b/tests/AnthropicClient.Tests/Unit/Models/StreamChatMessageRequestTests.cs
new file mode 100644
index 0000000..e2cc8d9
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/StreamChatMessageRequestTests.cs
@@ -0,0 +1,237 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class StreamChatMessageRequestTests : SerializationTest
+{
+  private readonly string _testJson = @"{
+    ""model"": ""claude-3-sonnet-20240229"",
+    ""system"": ""test-system"",
+    ""messages"": [
+      { ""role"": ""user"", ""content"": [{ ""text"": ""Hello!"", ""type"": ""text"" }] }
+    ],
+    ""max_tokens"": 512,
+    ""metadata"": { ""test"":""test"" },
+    ""stop_sequences"": [],
+    ""temperature"": 0.5,
+    ""topK"": 10,
+    ""topP"": 0.5,
+    ""tool_choice"": { ""type"":""auto"" },
+    ""tools"": [
+      {
+        ""name"": ""test-tool"",
+        ""description"": ""test-description"",
+        ""input_schema"": {
+          ""type"": ""object"",
+          ""properties"": {
+            ""test-property"": {
+              ""type"": ""string"",
+              ""description"": ""test-description""
+            }
+          },
+          ""required"": [""test-property""]
+        }
+      }
+    ],
+    ""stream"": true
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var model = AnthropicModels.Claude3Sonnet;
+    var messages = new List<ChatMessage> { new() };
+    var maxTokens = 512;
+    var system = "test-system";
+    var metadata = new Dictionary<string, object> { ["test"] = "test" };
+    var temperature = 0.5m;
+    var topK = 10;
+    var topP = 0.5m;
+    var toolChoice = new AutoToolChoice();
+    var tools = new List<Tool> { new() };
+
+    var chatMessageRequest = new StreamChatMessageRequest(
+      model: model,
+      messages: messages,
+      maxTokens: maxTokens,
+      system: system,
+      metadata: metadata,
+      temperature: temperature,
+      topK: topK,
+      topP: topP,
+      toolChoice: toolChoice,
+      tools: tools
+    );
+
+    chatMessageRequest.Model.Should().Be(model);
+    chatMessageRequest.Messages.Should().BeSameAs(messages);
+    chatMessageRequest.MaxTokens.Should().Be(maxTokens);
+    chatMessageRequest.System.Should().Be(system);
+    chatMessageRequest.Metadata.Should().BeSameAs(metadata);
+    chatMessageRequest.Temperature.Should().Be(temperature);
+    chatMessageRequest.TopK.Should().Be(topK);
+    chatMessageRequest.TopP.Should().Be(topP);
+    chatMessageRequest.ToolChoice.Should().Be(toolChoice);
+    chatMessageRequest.Tools.Should().BeSameAs(tools);
+    chatMessageRequest.Stream.Should().BeTrue();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledAndModelIsNull_ItShouldThrowArgumentNullException()
+  {
+    var action = () => new StreamChatMessageRequest(
+      model: null!,
+      messages: [new()]
+    );
+
+    action.Should().Throw<ArgumentNullException>();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledAndMessagesIsNull_ItShouldThrowArgumentNullException()
+  {
+    var action = () => new StreamChatMessageRequest(
+      model: AnthropicModels.Claude3Sonnet,
+      messages: null!
+    );
+
+    action.Should().Throw<ArgumentNullException>();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledAndModelIsInvalid_ItShouldThrowArgumentException()
+  {
+    var action = () => new StreamChatMessageRequest(
+      model: "invalid-model",
+      messages: [new()]
+    );
+
+    action.Should().Throw<ArgumentException>();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledAndMessagesIsEmpty_ItShouldThrowArgumentException()
+  {
+    var action = () => new StreamChatMessageRequest(
+      model: AnthropicModels.Claude3Sonnet,
+      messages: []
+    );
+
+    action.Should().Throw<ArgumentException>();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledAndMaxTokensIsInvalid_ItShouldThrowArgumentException()
+  {
+    var action = () => new StreamChatMessageRequest(
+      model: AnthropicModels.Claude3Sonnet,
+      messages: [new()],
+      maxTokens: 0
+    );
+
+    action.Should().Throw<ArgumentException>();
+  }
+
+  [Theory]
+  [InlineData(-1)]
+  [InlineData(2)]
+  public void Constructor_WhenCalledAndTemperatureIsInvalid_ItShouldThrowArgumentException(decimal temperature)
+  {
+    var action = () => new StreamChatMessageRequest(
+      model: AnthropicModels.Claude3Sonnet,
+      messages: [new()],
+      temperature: temperature
+    );
+
+    action.Should().Throw<ArgumentException>();
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var messages = new List<ChatMessage>()
+    {
+      new()
+      {
+        Role = MessageRole.User,
+        Content = [new TextContent("Hello!")]
+      }
+    };
+
+    var model = AnthropicModels.Claude3Sonnet;
+    var maxTokens = 512;
+    var system = "test-system";
+    var metadata = new Dictionary<string, object>
+    {
+      ["test"] = "test"
+    };
+    var temperature = 0.5m;
+    var topK = 10;
+    var topP = 0.5m;
+    var toolChoice = new AutoToolChoice();
+    var tools = new List<Tool>
+    {
+      new()
+      {
+        Name = "test-tool",
+        Description = "test-description",
+        InputSchema = new InputSchema(
+          properties: new Dictionary<string, InputProperty>
+          {
+            ["test-property"] = new InputProperty(
+              type: "string",
+              description: "test-description"
+            )
+          },
+          required: ["test-property"]
+        ),
+      }
+    };
+
+    var chatMessageRequest = new StreamChatMessageRequest(
+      model: model,
+      messages: messages,
+      maxTokens: maxTokens,
+      system: system,
+      metadata: metadata,
+      temperature: temperature,
+      topK: topK,
+      topP: topP,
+      toolChoice: toolChoice,
+      tools: tools
+    );
+
+    var actual = Serialize(chatMessageRequest);
+
+    JsonAssert.Equal(_testJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedShape()
+  {
+    var chatMessageRequest = Deserialize<StreamChatMessageRequest>(_testJson);
+
+    chatMessageRequest!.Model.Should().Be(AnthropicModels.Claude3Sonnet);
+    chatMessageRequest.System.Should().Be("test-system");
+    chatMessageRequest.Messages.Should().HaveCount(1);
+    chatMessageRequest.MaxTokens.Should().Be(512);
+    chatMessageRequest.Metadata.Should().HaveCount(1);
+
+    var testValue = chatMessageRequest.Metadata!.GetValueOrDefault("test")!.ToString();
+    testValue.Should().Be("test");
+
+    chatMessageRequest.Temperature.Should().Be(0.5m);
+    chatMessageRequest.TopK.Should().Be(10);
+    chatMessageRequest.TopP.Should().Be(0.5m);
+    chatMessageRequest.ToolChoice.Should().BeOfType<AutoToolChoice>();
+    chatMessageRequest.ToolChoice!.Type.Should().Be("auto");
+    chatMessageRequest.Tools.Should().HaveCount(1);
+    chatMessageRequest.Tools![0].Name.Should().Be("test-tool");
+    chatMessageRequest.Tools[0].Description.Should().Be("test-description");
+    chatMessageRequest.Tools[0].InputSchema.Type.Should().Be("object");
+    chatMessageRequest.Tools[0].InputSchema.Properties.Should().HaveCount(1);
+    chatMessageRequest.Tools[0].InputSchema.Properties["test-property"].Type.Should().Be("string");
+    chatMessageRequest.Tools[0].InputSchema.Properties["test-property"].Description.Should().Be("test-description");
+    chatMessageRequest.Tools[0].InputSchema.Required.Should().HaveCount(1);
+    chatMessageRequest.Tools[0].InputSchema.Required[0].Should().Be("test-property");
+    chatMessageRequest.Stream.Should().BeTrue();
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/TextDeltaTests.cs b/tests/AnthropicClient.Tests/Unit/Models/TextDeltaTests.cs
new file mode 100644
index 0000000..9f68a64
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Models/TextDeltaTests.cs
@@ -0,0 +1,40 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class TextDeltaTests : SerializationTest
+{
+  private readonly string _testJson = @"{
+    ""type"": ""text_delta"",
+    ""text"": ""Hello World!""
+  }";
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldInitializeProperties()
+  {
+    var text = "Hello World!";
+    
+    var textDelta = new TextDelta(text);
+    
+    textDelta.Type.Should().Be("text_delta");
+    textDelta.Text.Should().Be(text);
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var textDelta = new TextDelta("Hello World!");
+
+    var actual = Serialize(textDelta);
+  
+    JsonAssert.Equal(_testJson, actual);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedProperties()
+  {
+    var expected = new TextDelta("Hello World!");
+
+    var actual = Deserialize<TextDelta>(_testJson);
+
+    actual.Should().BeEquivalentTo(expected);
+  }
+}
\ No newline at end of file