fix: add missing type property to image source model

tests/AnthropicClient.Tests/AnthropicClient.Tests.csproj

@@ -6,6 +6,7 @@
     <Nullable>enable</Nullable>
     <IsPackable>false</IsPackable>
     <IsTestProject>true</IsTestProject>
+    <NoWarn>$(NoWarn);IDE0039</NoWarn>
   </PropertyGroup>
 
   <ItemGroup>

tests/AnthropicClient.Tests/Unit/Models/ImageSourceTests.cs

@@ -0,0 +1,60 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class ImageSourceTests
+{
+  [Fact]
+  public void Constructor_WhenCalledWithValidArguments_ItShouldSetProperties()
+  {
+    var mediaType = "image/jpeg";
+    var data = "base64data";
+
+    var imageSource = new ImageSource(mediaType, data);
+
+    imageSource.MediaType.Should().Be(mediaType);
+    imageSource.Data.Should().Be(data);
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledWithInvalidMediaType_ItShouldThrowArgumentException()
+  {
+    var mediaType = "invalid";
+    var data = "base64data";
+
+    var action = () => new ImageSource(mediaType, data);
+
+    action.Should().Throw<ArgumentException>();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledWithNullMediaType_ItShouldThrowArgumentNullException()
+  {
+    string? mediaType = null;
+    var data = "base64data";
+
+    var action = () => new ImageSource(mediaType!, data);
+
+    action.Should().Throw<ArgumentNullException>();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalledWithNullData_ItShouldThrowArgumentNullException()
+  {
+    var mediaType = "image/jpeg";
+    string? data = null;
+
+    var action = () => new ImageSource(mediaType, data!);
+
+    action.Should().Throw<ArgumentNullException>();
+  }
+
+  [Fact]
+  public void Constructor_WhenCalled_ItShouldHaveTypePropertySetToBase64()
+  {
+    var mediaType = "image/jpeg";
+    var data = "base64data";
+
+    var imageSource = new ImageSource(mediaType, data);
+
+    imageSource.Type.Should().Be("base64");
+  }
+}