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/ElicitRequestParamsTests.cs

@@ -0,0 +1,89 @@
+using ModelContextProtocol.Protocol;
+using System.Text.Json;
+using System.Text.Json.Nodes;
+
+namespace ModelContextProtocol.Tests.Protocol;
+
+public static class ElicitRequestParamsTests
+{
+    [Fact]
+    public static void ElicitRequestParams_SerializationRoundTrip_PreservesAllProperties()
+    {
+        var original = new ElicitRequestParams
+        {
+            Mode = "form",
+            ElicitationId = "elicit-123",
+            Url = null,
+            Message = "Please provide your details",
+            RequestedSchema = new ElicitRequestParams.RequestSchema
+            {
+                Properties =
+                {
+                    ["name"] = new ElicitRequestParams.StringSchema { Description = "Your name" },
+                    ["age"] = new ElicitRequestParams.NumberSchema { Description = "Your age" }
+                }
+            },
+            Task = new McpTaskMetadata { TimeToLive = TimeSpan.FromMinutes(10) },
+            Meta = new JsonObject { ["progressToken"] = "tok-1" }
+        };
+
+        string json = JsonSerializer.Serialize(original, McpJsonUtilities.DefaultOptions);
+        var deserialized = JsonSerializer.Deserialize<ElicitRequestParams>(json, McpJsonUtilities.DefaultOptions);
+
+        Assert.NotNull(deserialized);
+        Assert.Equal("form", deserialized.Mode);
+        Assert.Equal("elicit-123", deserialized.ElicitationId);
+        Assert.Null(deserialized.Url);
+        Assert.Equal("Please provide your details", deserialized.Message);
+        Assert.NotNull(deserialized.RequestedSchema);
+        Assert.Equal(2, deserialized.RequestedSchema.Properties.Count);
+        Assert.NotNull(deserialized.Task);
+        Assert.Equal(TimeSpan.FromMinutes(10), deserialized.Task.TimeToLive);
+        Assert.NotNull(deserialized.Meta);
+        Assert.Equal("tok-1", (string)deserialized.Meta["progressToken"]!);
+    }
+
+    [Fact]
+    public static void ElicitRequestParams_SerializationRoundTrip_UrlMode()
+    {
+        var original = new ElicitRequestParams
+        {
+            Mode = "url",
+            ElicitationId = "elicit-456",
+            Url = "https://example.com/auth",
+            Message = "Please authenticate"
+        };
+
+        string json = JsonSerializer.Serialize(original, McpJsonUtilities.DefaultOptions);
+        var deserialized = JsonSerializer.Deserialize<ElicitRequestParams>(json, McpJsonUtilities.DefaultOptions);
+
+        Assert.NotNull(deserialized);
+        Assert.Equal("url", deserialized.Mode);
+        Assert.Equal("elicit-456", deserialized.ElicitationId);
+        Assert.Equal("https://example.com/auth", deserialized.Url);
+        Assert.Equal("Please authenticate", deserialized.Message);
+        Assert.Null(deserialized.RequestedSchema);
+        Assert.Null(deserialized.Task);
+    }
+
+    [Fact]
+    public static void ElicitRequestParams_SerializationRoundTrip_WithMinimalProperties()
+    {
+        var original = new ElicitRequestParams
+        {
+            Message = "Confirm action"
+        };
+
+        string json = JsonSerializer.Serialize(original, McpJsonUtilities.DefaultOptions);
+        var deserialized = JsonSerializer.Deserialize<ElicitRequestParams>(json, McpJsonUtilities.DefaultOptions);
+
+        Assert.NotNull(deserialized);
+        Assert.Equal("form", deserialized.Mode);
+        Assert.Equal("Confirm action", deserialized.Message);
+        Assert.Null(deserialized.ElicitationId);
+        Assert.Null(deserialized.Url);
+        Assert.Null(deserialized.RequestedSchema);
+        Assert.Null(deserialized.Task);
+        Assert.Null(deserialized.Meta);
+    }
+}