tests: add additional test coverage

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

@@ -1,7 +1,13 @@
 namespace AnthropicClient.Tests.Unit.Models;
 
-public class TextSourceTests
+public class TextSourceTests : SerializationTest
 {
+  private readonly string _testJson = @"{
+    ""type"": ""text"",
+    ""media_type"": ""text/plain"",
+    ""data"": ""data""
+  }";
+
   [Fact]
   public void Constructor_WhenCalled_ItShouldSetProperties()
   {
@@ -11,4 +17,25 @@ public class TextSourceTests
     result.MediaType.Should().Be("text/plain");
     result.Data.Should().Be("data");
   }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var source = new TextSource("data");
+
+    var result = Serialize<Source>(source);
+
+    JsonAssert.Equal(_testJson, result);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedShape()
+  {
+    var source = Deserialize<Source>(_testJson);
+
+    var textSource = source.As<TextSource>();
+    textSource!.Type.Should().Be("text");
+    textSource.MediaType.Should().Be("text/plain");
+    textSource.Data.Should().Be("data");
+  }
 }