Default draft protocol support: sessionless + handshake-less (SEP-2575 + SEP-2567) (#1610)

tests/ModelContextProtocol.Tests/Client/DraftConnectionTests.cs

@@ -0,0 +1,91 @@
+using Microsoft.Extensions.DependencyInjection;
+using ModelContextProtocol.Client;
+using ModelContextProtocol.Protocol;
+using ModelContextProtocol.Server;
+using System.Text.Json;
+
+namespace ModelContextProtocol.Tests.Client;
+
+/// <summary>
+/// Tests for the draft protocol revision (SEP-2575 + SEP-2567) connection flow on
+/// <see cref="McpClient"/> — the client should call <c>server/discover</c> instead of
+/// <c>initialize</c> when <see cref="McpClientOptions.ProtocolVersion"/> is set to
+/// <see cref="McpSessionHandler.DraftProtocolVersion"/>.
+/// </summary>
+public class DraftConnectionTests : ClientServerTestBase
+{
+    private const string DraftVersion = McpHttpHeaders.DraftProtocolVersion;
+    private const string LatestStableVersion = "2025-11-25";
+
+    public DraftConnectionTests(ITestOutputHelper testOutputHelper)
+        : base(testOutputHelper, startServer: false)
+    {
+    }
+
+    protected override void ConfigureServices(ServiceCollection services, IMcpServerBuilder mcpServerBuilder)
+    {
+        services.Configure<McpServerOptions>(options =>
+        {
+            options.ServerInfo = new Implementation { Name = nameof(DraftConnectionTests), Version = "1.0" };
+        });
+    }
+
+    [Fact]
+    public async Task DraftClient_ConnectingToDraftServer_NegotiatesDraftVersion()
+    {
+        StartServer();
+
+        var options = new McpClientOptions { ProtocolVersion = DraftVersion };
+        await using var client = await CreateMcpClientForServer(options);
+
+        Assert.Equal(DraftVersion, client.NegotiatedProtocolVersion);
+        Assert.NotNull(client.ServerCapabilities);
+        Assert.Equal(nameof(DraftConnectionTests), client.ServerInfo.Name);
+    }
+
+    [Fact]
+    public async Task LegacyClient_ConnectingToDraftServer_NegotiatesLegacyVersion()
+    {
+        StartServer();
+
+        await using var client = await CreateMcpClientForServer(new McpClientOptions { ProtocolVersion = LatestStableVersion });
+
+        Assert.NotEqual(DraftVersion, client.NegotiatedProtocolVersion);
+    }
+
+    [Fact]
+    public async Task LegacyClient_CanCallServerDiscover()
+    {
+        // server/discover is registered unconditionally, so a legacy client can probe it
+        // (e.g., to learn capabilities without doing a second initialize).
+        StartServer();
+
+        await using var client = await CreateMcpClientForServer(new McpClientOptions { ProtocolVersion = LatestStableVersion });
+
+        var response = await client.SendRequestAsync(
+            new JsonRpcRequest { Method = RequestMethods.ServerDiscover },
+            TestContext.Current.CancellationToken);
+
+        var discoverResult = JsonSerializer.Deserialize<DiscoverResult>(response.Result, McpJsonUtilities.DefaultOptions);
+        Assert.NotNull(discoverResult);
+        Assert.NotEmpty(discoverResult.SupportedVersions);
+        Assert.Contains(LatestStableVersion, discoverResult.SupportedVersions);
+        Assert.Equal(nameof(DraftConnectionTests), discoverResult.ServerInfo.Name);
+    }
+
+    [Fact]
+    public async Task DraftServer_DiscoverIncludesDraftVersion()
+    {
+        StartServer();
+
+        await using var client = await CreateMcpClientForServer();
+
+        var response = await client.SendRequestAsync(
+            new JsonRpcRequest { Method = RequestMethods.ServerDiscover },
+            TestContext.Current.CancellationToken);
+
+        var discoverResult = JsonSerializer.Deserialize<DiscoverResult>(response.Result, McpJsonUtilities.DefaultOptions);
+        Assert.NotNull(discoverResult);
+        Assert.Contains(DraftVersion, discoverResult.SupportedVersions);
+    }
+}