tests: add additional test coverage

tests/AnthropicClient.Tests/Unit/Models/Base64SourceTests.cs

@@ -1,7 +1,13 @@
 namespace AnthropicClient.Tests.Unit.Models;
 
-public class Base64SourceTests
+public class Base64SourceTests : SerializationTest
 {
+  private readonly string _testJson = @"{
+    ""type"": ""base64"",
+    ""media_type"": ""application/pdf"",
+    ""data"": ""base64data""
+  }";
+
   [Fact]
   public void Constructor_WhenCalledWithValidArguments_ItShouldSetProperties()
   {
@@ -36,4 +42,47 @@ public class Base64SourceTests
 
     action.Should().Throw<ArgumentNullException>();
   }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var mediaType = "application/pdf";
+    var data = "base64data";
+    var source = new Base64Source(mediaType, data);
+
+    var result = Serialize<Source>(source);
+
+    JsonAssert.Equal(_testJson, result);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedShape()
+  {
+    var source = Deserialize<Source>(_testJson);
+
+    var base64Source = source.As<Base64Source>();
+    base64Source!.Type.Should().Be("base64");
+    base64Source.MediaType.Should().Be("application/pdf");
+    base64Source.Data.Should().Be("base64data");
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenMediaTypeIsMissing_ItShouldThrowException()
+  {
+    var json = @"{ ""type"": ""base64"", ""data"": ""base64data"" }";
+
+    var action = () => Deserialize<Source>(json);
+
+    action.Should().Throw<JsonException>();
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenMediaTypeIsNull_ItShouldThrowException()
+  {
+    var json = @"{ ""type"": ""base64"", ""media_type"": null, ""data"": ""base64data"" }";
+
+    var action = () => Deserialize<Source>(json);
+
+    action.Should().Throw<JsonException>();
+  }
 }