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Follow-ups to #1610: de-draft 2026-07-28 terminology, renumber error codes, ProtocolVersion floor (#1671)

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Stephen Halter 2026-06-25 14:07:52 -07:00 • committed by GitHub
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tests/ModelContextProtocol.AspNetCore.Tests/DraftStatefulFallbackTests.cs
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@ -1,130 +0,0 @@
using Microsoft.AspNetCore.Builder;
using Microsoft.Extensions.DependencyInjection;
using ModelContextProtocol.AspNetCore.Tests.Utils;
using ModelContextProtocol.Client;
using ModelContextProtocol.Protocol;
using ModelContextProtocol.Server;
using ModelContextProtocol.Tests.Utils;
using System.Text.Json;
namespace ModelContextProtocol.AspNetCore.Tests;
/// <summary>
/// End-to-end coverage for a default (draft-first) client connecting to a real C# Streamable HTTP
/// server that deliberately opted into sessions (<see cref="HttpServerTransportOptions.Stateless"/>
/// is <c>false</c>). Draft is sessionless (SEP-2567 / SEP-2575), so the server refuses the
/// sessionless draft probe with <c>-32004 UnsupportedProtocolVersion</c>. The client must then
/// auto-downgrade to the legacy <c>initialize</c> handshake, obtain the stateful session the server
/// author opted into, and continue to work — including a server→client elicitation round-trip
/// resolved over the stateful session via the legacy backcompat resolver.
/// </summary>
public class DraftStatefulFallbackTests(ITestOutputHelper outputHelper) : KestrelInMemoryTest(outputHelper), IAsyncDisposable
{
private WebApplication? _app;
public async ValueTask DisposeAsync()
{
if (_app is not null)
{
await _app.DisposeAsync();
}
base.Dispose();
}
[McpServerTool(Name = "greet")]
private static string Greet([System.ComponentModel.Description("Name to greet")] string name) => $"Hello, {name}!";
[McpServerTool(Name = "greet_via_elicit")]
private static async Task<string> GreetViaElicit(McpServer server, CancellationToken cancellationToken)
{
// Server→client round-trip: only works when the session is stateful, which is exactly what
// the legacy fallback re-establishes for the draft-first client.
var elicitResult = await server.ElicitAsync(new ElicitRequestParams
{
Message = "What is your name?",
RequestedSchema = new(),
}, cancellationToken);
var name = elicitResult.Content?.TryGetValue("answer", out var answer) == true
? answer.GetString()
: "stranger";
return $"Hello, {name}!";
}
private async Task StartStatefulServerAsync()
{
Builder.Services.AddMcpServer(options =>
{
options.ServerInfo = new Implementation { Name = nameof(DraftStatefulFallbackTests), Version = "1" };
})
// Stateless = false is a deliberate opt-in to sessions. Draft can never be served
// statefully, so the server refuses the sessionless draft probe and the client downgrades.
.WithHttpTransport(options => options.Stateless = false)
.WithTools([McpServerTool.Create(Greet), McpServerTool.Create(GreetViaElicit)]);
_app = Builder.Build();
_app.MapMcp();
await _app.StartAsync(TestContext.Current.CancellationToken);
}
private async Task<McpClient> ConnectDefaultClientAsync(Action<McpClientOptions>? configureClient = null)
{
await using var transport = new HttpClientTransport(new HttpClientTransportOptions
{
Endpoint = new Uri("http://localhost:5000/"),
TransportMode = HttpTransportMode.StreamableHttp,
}, HttpClient, LoggerFactory);
// Default options: ProtocolVersion is null, which now prefers the draft revision and probes
// with server/discover before falling back to a legacy initialize handshake.
var clientOptions = new McpClientOptions();
configureClient?.Invoke(clientOptions);
return await McpClient.CreateAsync(transport, clientOptions, LoggerFactory, TestContext.Current.CancellationToken);
}
[Fact]
public async Task DefaultDraftClient_AgainstStatefulServer_DowngradesToLegacy_AndToolsWork()
{
await StartStatefulServerAsync();
await using var client = await ConnectDefaultClientAsync();
// The sessionless draft probe was refused (-32004), so the client downgraded to legacy.
Assert.Equal("2025-11-25", client.NegotiatedProtocolVersion);
var result = await client.CallToolAsync("greet",
new Dictionary<string, object?> { ["name"] = "Alice" },
cancellationToken: TestContext.Current.CancellationToken);
var text = Assert.IsType<TextContentBlock>(Assert.Single(result.Content)).Text;
Assert.Equal("Hello, Alice!", text);
}
[Fact]
public async Task DefaultDraftClient_AgainstStatefulServer_ServerToClientElicitation_RoundTrips()
{
await StartStatefulServerAsync();
await using var client = await ConnectDefaultClientAsync(options =>
{
options.Handlers.ElicitationHandler = (request, ct) => new ValueTask<ElicitResult>(new ElicitResult
{
Action = "accept",
Content = new Dictionary<string, JsonElement>
{
["answer"] = JsonDocument.Parse("\"Bob\"").RootElement.Clone(),
},
});
});
Assert.Equal("2025-11-25", client.NegotiatedProtocolVersion);
var result = await client.CallToolAsync("greet_via_elicit",
cancellationToken: TestContext.Current.CancellationToken);
var text = Assert.IsType<TextContentBlock>(Assert.Single(result.Content)).Text;
Assert.Equal("Hello, Bob!", text);
Assert.True(result.IsError is not true);
}
}