Add serialization roundtrip tests for all Protocol namespace types (#1289)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

tests/ModelContextProtocol.Tests/Protocol/RequestMcpTasksCapabilityTests.cs

@@ -0,0 +1,108 @@
+using ModelContextProtocol.Protocol;
+using System.Text.Json;
+
+namespace ModelContextProtocol.Tests.Protocol;
+
+public static class RequestMcpTasksCapabilityTests
+{
+    [Fact]
+    public static void RequestMcpTasksCapability_SerializationRoundTrip_ToolsOnly()
+    {
+        // Arrange
+        var original = new RequestMcpTasksCapability
+        {
+            Tools = new ToolsMcpTasksCapability
+            {
+                Call = new CallToolMcpTasksCapability()
+            }
+        };
+
+        // Act
+        string json = JsonSerializer.Serialize(original, McpJsonUtilities.DefaultOptions);
+        var deserialized = JsonSerializer.Deserialize<RequestMcpTasksCapability>(json, McpJsonUtilities.DefaultOptions);
+
+        // Assert
+        Assert.NotNull(deserialized);
+        Assert.NotNull(deserialized.Tools);
+        Assert.NotNull(deserialized.Tools.Call);
+        Assert.Null(deserialized.Sampling);
+        Assert.Null(deserialized.Elicitation);
+    }
+
+    [Fact]
+    public static void RequestMcpTasksCapability_SerializationRoundTrip_SamplingOnly()
+    {
+        // Arrange
+        var original = new RequestMcpTasksCapability
+        {
+            Sampling = new SamplingMcpTasksCapability
+            {
+                CreateMessage = new CreateMessageMcpTasksCapability()
+            }
+        };
+
+        // Act
+        string json = JsonSerializer.Serialize(original, McpJsonUtilities.DefaultOptions);
+        var deserialized = JsonSerializer.Deserialize<RequestMcpTasksCapability>(json, McpJsonUtilities.DefaultOptions);
+
+        // Assert
+        Assert.NotNull(deserialized);
+        Assert.Null(deserialized.Tools);
+        Assert.NotNull(deserialized.Sampling);
+        Assert.NotNull(deserialized.Sampling.CreateMessage);
+        Assert.Null(deserialized.Elicitation);
+    }
+
+    [Fact]
+    public static void RequestMcpTasksCapability_SerializationRoundTrip_ElicitationOnly()
+    {
+        // Arrange
+        var original = new RequestMcpTasksCapability
+        {
+            Elicitation = new ElicitationMcpTasksCapability
+            {
+                Create = new CreateElicitationMcpTasksCapability()
+            }
+        };
+
+        // Act
+        string json = JsonSerializer.Serialize(original, McpJsonUtilities.DefaultOptions);
+        var deserialized = JsonSerializer.Deserialize<RequestMcpTasksCapability>(json, McpJsonUtilities.DefaultOptions);
+
+        // Assert
+        Assert.NotNull(deserialized);
+        Assert.Null(deserialized.Tools);
+        Assert.Null(deserialized.Sampling);
+        Assert.NotNull(deserialized.Elicitation);
+        Assert.NotNull(deserialized.Elicitation.Create);
+    }
+
+    [Fact]
+    public static void RequestMcpTasksCapability_HasCorrectJsonPropertyNames()
+    {
+        var capability = new RequestMcpTasksCapability
+        {
+            Tools = new ToolsMcpTasksCapability
+            {
+                Call = new CallToolMcpTasksCapability()
+            },
+            Sampling = new SamplingMcpTasksCapability
+            {
+                CreateMessage = new CreateMessageMcpTasksCapability()
+            },
+            Elicitation = new ElicitationMcpTasksCapability
+            {
+                Create = new CreateElicitationMcpTasksCapability()
+            }
+        };
+
+        string json = JsonSerializer.Serialize(capability, McpJsonUtilities.DefaultOptions);
+
+        Assert.Contains("\"tools\":", json);
+        Assert.Contains("\"sampling\":", json);
+        Assert.Contains("\"elicitation\":", json);
+        Assert.Contains("\"call\":", json);
+        Assert.Contains("\"createMessage\":", json);
+        Assert.Contains("\"create\":", json);
+    }
+}