Reorganize MRTR tests by what they actually test

Move server-behavior tests from Client/ to Server/ and drop the
misleading McpClient prefix. Most MRTR tests verify server-side
behavior (handler lifecycle, backcompat resolution, low-level API)
but were in Client/ because they use ClientServerTestBase.

Split McpClientMrtrTests (17 tests) into:
- Client/MrtrIntegrationTests: E2E round-trips and client retry (10)
- Server/MrtrHandlerLifecycleTests: cancellation, disposal, logging (7)

Rename and move to Server/:
- McpClientMrtrCompatTests → MrtrBackcompatTests
- McpClientMrtrLowLevelTests → MrtrLowLevelApiTests
- McpClientMrtrMessageFilterTests → MrtrMessageFilterTests
- McpClientMrtrSessionLimitTests → MrtrSessionLimitTests
- McpClientMrtrWithTasksTests → MrtrTaskIntegrationTests

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: halter73

src/ModelContextProtocol.Core/Server/McpServerImpl.cs

@@ -1249,9 +1249,9 @@ private void WrapHandlerWithMrtr(string method)
                         inputResponses = JsonSerializer.Deserialize(responsesNode, McpJsonUtilities.JsonContext.Default.IDictionaryStringInputResponse);
                     }
 
-                    var nextExchangeTask = existingContinuation.MrtrContext.ResetForNextExchange(existingContinuation.PendingExchange!);
-
                     var exchange = existingContinuation.PendingExchange!;
+                    var nextExchangeTask = existingContinuation.MrtrContext.ResetForNextExchange(exchange);
+
                     if (inputResponses is not null &&
                         inputResponses.TryGetValue(exchange.Key, out var response))
                     {

tests/ModelContextProtocol.AspNetCore.Tests/MrtrProtocolTests.cs

@@ -858,8 +858,19 @@ public async Task SessionDelete_CancelsPendingMrtrContinuation()
         using var deleteResponse = await HttpClient.DeleteAsync("", TestContext.Current.CancellationToken);
         Assert.Equal(HttpStatusCode.OK, deleteResponse.StatusCode);
 
-        // Allow a moment for the async cancellation to propagate through the handler task.
-        await Task.Delay(100, TestContext.Current.CancellationToken);
+        // Poll for the async cancellation to propagate through the handler task.
+        // Under thread pool starvation, this can take significantly longer than 100ms.
+        var deadline = DateTime.UtcNow.AddSeconds(30);
+        while (true)
+        {
+            if (MockLoggerProvider.LogMessages.Any(m => m.Message.Contains("pending MRTR continuation"))
+                || DateTime.UtcNow >= deadline)
+            {
+                break;
+            }
+
+            await Task.Delay(100, TestContext.Current.CancellationToken);
+        }
 
         // 3. Verify that the MRTR cancellation was logged at Debug level.
         var mrtrCancelledLog = MockLoggerProvider.LogMessages

tests/ModelContextProtocol.Tests/Client/McpClientDeferredTaskCreationTests.cs

@@ -205,7 +205,7 @@ public async Task DeferredTaskCreation_ElicitThenCreateTask_ReturnsTaskResult()
         Assert.NotEmpty(result.Task.TaskId);
 
         // Wait for the tool to finish in the background.
-        await _toolAfterTaskCreation.Task.WaitAsync(TimeSpan.FromSeconds(10), TestContext.Current.CancellationToken);
+        await _toolAfterTaskCreation.Task.WaitAsync(TimeSpan.FromSeconds(30), TestContext.Current.CancellationToken);
         var taskStatus = await WaitForTaskCompletionAsync(result.Task.TaskId);
         Assert.Equal(McpTaskStatus.Completed, taskStatus.Status);
     }

…tocol.Tests/Client/McpClientMrtrTests.cs …col.Tests/Client/MrtrIntegrationTests.cstests/ModelContextProtocol.Tests/Client/McpClientMrtrTests.cs renamed to tests/ModelContextProtocol.Tests/Client/MrtrIntegrationTests.cs tests/ModelContextProtocol.Tests/Client/McpClientMrtrTests.cs renamed to tests/ModelContextProtocol.Tests/Client/MrtrIntegrationTests.cs

@@ -6,16 +6,17 @@
 using ModelContextProtocol.Tests.Utils;
 using System.Text.Json;
 
-namespace ModelContextProtocol.Tests.Client;
+namespace ModelContextProtocol.Tests.Server;
 
 /// <summary>
-/// Tests for MRTR compatibility across different experimental/non-experimental combinations.
-/// This test class configures the server WITHOUT ExperimentalProtocolVersion to test scenarios
-/// where the server is not opted-in to the experimental protocol.
+/// Tests for the server's backward-compatible resolution of MRTR-native tools.
+/// Verifies that when a tool throws IncompleteResultException and the client doesn't support MRTR,
+/// the server resolves input requests via standard JSON-RPC calls (elicitation, sampling, roots)
+/// and retries the handler.
 /// </summary>
-public class McpClientMrtrCompatTests : ClientServerTestBase
+public class MrtrBackcompatTests : ClientServerTestBase
 {
-    public McpClientMrtrCompatTests(ITestOutputHelper testOutputHelper)
+    public MrtrBackcompatTests(ITestOutputHelper testOutputHelper)
         : base(testOutputHelper, startServer: false)
     {
     }

…Tests/Client/McpClientMrtrCompatTests.cs …ocol.Tests/Server/MrtrBackcompatTests.cstests/ModelContextProtocol.Tests/Client/McpClientMrtrCompatTests.cs renamed to tests/ModelContextProtocol.Tests/Server/MrtrBackcompatTests.cs tests/ModelContextProtocol.Tests/Client/McpClientMrtrCompatTests.cs renamed to tests/ModelContextProtocol.Tests/Server/MrtrBackcompatTests.cs

@@ -5,15 +5,15 @@
 using ModelContextProtocol.Server;
 using System.Text.Json;
 
-namespace ModelContextProtocol.Tests.Client;
+namespace ModelContextProtocol.Tests.Server;
 
 /// <summary>
-/// Integration tests for the low-level MRTR API where tool handlers directly throw
-/// <see cref="IncompleteResultException"/> and manage request state themselves.
+/// Tests for the low-level MRTR server API — IsMrtrSupported, IncompleteResultException,
+/// and client auto-retry of incomplete results.
 /// </summary>
-public class McpClientMrtrLowLevelTests : ClientServerTestBase
+public class MrtrLowLevelApiTests : ClientServerTestBase
 {
-    public McpClientMrtrLowLevelTests(ITestOutputHelper testOutputHelper)
+    public MrtrLowLevelApiTests(ITestOutputHelper testOutputHelper)
         : base(testOutputHelper, startServer: false)
     {
     }

tests/ModelContextProtocol.Tests/Server/MrtrHandlerLifecycleTests.cs

@@ -7,17 +7,18 @@
 using System.Collections.Concurrent;
 using System.Text.Json;
 
-namespace ModelContextProtocol.Tests.Client;
+namespace ModelContextProtocol.Tests.Server;
 
 /// <summary>
-/// Tests that verify transport middleware sees raw MRTR JSON-RPC messages and
-/// that old-style sampling/elicitation JSON-RPC requests are NOT sent when MRTR is active.
+/// Tests that message filters correctly observe MRTR protocol behavior — verifying that
+/// IncompleteResult responses are visible to outgoing filters, and that no legacy
+/// elicitation/sampling requests are sent when MRTR is active.
 /// </summary>
-public class McpClientMrtrMessageFilterTests : ClientServerTestBase
+public class MrtrMessageFilterTests : ClientServerTestBase
 {
     private readonly ConcurrentBag<string> _outgoingRequestMethods = [];
 
-    public McpClientMrtrMessageFilterTests(ITestOutputHelper testOutputHelper)
+    public MrtrMessageFilterTests(ITestOutputHelper testOutputHelper)
         : base(testOutputHelper, startServer: false)
     {
     }

…sts/Client/McpClientMrtrLowLevelTests.cs …col.Tests/Server/MrtrLowLevelApiTests.cstests/ModelContextProtocol.Tests/Client/McpClientMrtrLowLevelTests.cs renamed to tests/ModelContextProtocol.Tests/Server/MrtrLowLevelApiTests.cs tests/ModelContextProtocol.Tests/Client/McpClientMrtrLowLevelTests.cs renamed to tests/ModelContextProtocol.Tests/Server/MrtrLowLevelApiTests.cs

@@ -7,14 +7,13 @@
 using System.Collections.Concurrent;
 using System.Text.Json.Nodes;
 
-namespace ModelContextProtocol.Tests.Client;
+namespace ModelContextProtocol.Tests.Server;
 
 /// <summary>
-/// Tests proving that outgoing message filters can track and limit per-session MRTR flows.
-/// This demonstrates that protocol-level sessions enable session-scoped resource governance
-/// that would not be possible without the Mcp-Session-Id routing mechanism.
+/// Tests for session-scoped MRTR resource governance — verifying that outgoing message
+/// filters can track and limit MRTR round trips per session.
 /// </summary>
-public class McpClientMrtrSessionLimitTests : ClientServerTestBase
+public class MrtrSessionLimitTests : ClientServerTestBase
 {
     /// <summary>
     /// Tracks the number of pending MRTR flows per session. Incremented when an IncompleteResult
@@ -39,7 +38,7 @@ public class McpClientMrtrSessionLimitTests : ClientServerTestBase
     /// </summary>
     private int _blockedFlowCount;
 
-    public McpClientMrtrSessionLimitTests(ITestOutputHelper testOutputHelper)
+    public MrtrSessionLimitTests(ITestOutputHelper testOutputHelper)
         : base(testOutputHelper, startServer: false)
     {
     }

…lient/McpClientMrtrMessageFilterTests.cs …l.Tests/Server/MrtrMessageFilterTests.cstests/ModelContextProtocol.Tests/Client/McpClientMrtrMessageFilterTests.cs renamed to tests/ModelContextProtocol.Tests/Server/MrtrMessageFilterTests.cs tests/ModelContextProtocol.Tests/Client/McpClientMrtrMessageFilterTests.cs renamed to tests/ModelContextProtocol.Tests/Server/MrtrMessageFilterTests.cs

@@ -5,16 +5,16 @@
 using ModelContextProtocol.Server;
 using ModelContextProtocol.Tests.Utils;
 
-namespace ModelContextProtocol.Tests.Client;
+namespace ModelContextProtocol.Tests.Server;
 
 /// <summary>
-/// Tests for MRTR (Multi Round-Trip Requests) interacting with the Task system.
-/// Verifies that task status tracking works correctly during MRTR-resolved sampling/elicitation,
-/// and that task-based methods (SampleAsTaskAsync/ElicitAsTaskAsync) bypass MRTR interception.
+/// Tests for the interaction between MRTR and the Tasks feature — verifying that MRTR-driven
+/// tool calls correctly track task status (InputRequired), and that task-based sampling
+/// bypasses MRTR interception.
 /// </summary>
-public class McpClientMrtrWithTasksTests : ClientServerTestBase
+public class MrtrTaskIntegrationTests : ClientServerTestBase
 {
-    public McpClientMrtrWithTasksTests(ITestOutputHelper testOutputHelper)
+    public MrtrTaskIntegrationTests(ITestOutputHelper testOutputHelper)
         : base(testOutputHelper, startServer: false)
     {
     }