Add private protected ctors to McpClient and McpServer to prevent external derivation

src/ModelContextProtocol.Core/Client/McpClient.cs

@@ -7,6 +7,11 @@ namespace ModelContextProtocol.Client;
 /// </summary>
 public abstract partial class McpClient : McpSession
 {
+    /// <summary>Initializes a new instance of the <see cref="McpClient"/> class.</summary>
+    private protected McpClient()
+    {
+    }
+
     /// <summary>
     /// Gets the capabilities supported by the connected server.
     /// </summary>

src/ModelContextProtocol.Core/Server/McpServer.cs

@@ -7,6 +7,11 @@ namespace ModelContextProtocol.Server;
 /// </summary>
 public abstract partial class McpServer : McpSession
 {
+    /// <summary>Initializes a new instance of the <see cref="McpServer"/> class.</summary>
+    private protected McpServer()
+    {
+    }
+
     /// <summary>
     /// Gets the capabilities supported by the client.
     /// </summary>

tests/Common/Utils/TestServerTransport.cs

@@ -93,10 +93,11 @@ await WriteMessageAsync(new JsonRpcResponse
         else
         {
             // Return a normal sampling response
+            var result = MockSamplingResult ?? new CreateMessageResult { Content = [new TextContentBlock { Text = "" }], Model = "model" };
             await WriteMessageAsync(new JsonRpcResponse
             {
                 Id = request.Id,
-                Result = JsonSerializer.SerializeToNode(new CreateMessageResult { Content = [new TextContentBlock { Text = "" }], Model = "model" }, McpJsonUtilities.DefaultOptions),
+                Result = JsonSerializer.SerializeToNode(result, McpJsonUtilities.DefaultOptions),
             }, cancellationToken);
         }
     }
@@ -125,6 +126,12 @@ await WriteMessageAsync(new JsonRpcResponse
         }
     }
 
+    /// <summary>
+    /// Gets or sets the sampling result to return from sampling/createMessage requests.
+    /// When null, a default sampling response is returned.
+    /// </summary>
+    public CreateMessageResult? MockSamplingResult { get; set; }
+
     /// <summary>
     /// Gets or sets the task to return from tasks/get requests.
     /// </summary>

tests/ModelContextProtocol.Tests/Configuration/McpServerBuilderExtensionsPromptsTests.cs

@@ -5,7 +5,7 @@
 using ModelContextProtocol.Client;
 using ModelContextProtocol.Protocol;
 using ModelContextProtocol.Server;
-using Moq;
+using ModelContextProtocol.Tests.Utils;
 using System.Collections;
 using System.ComponentModel;
 using System.Text.Json;
@@ -314,7 +314,7 @@ public async Task WithPrompts_TargetInstance_UsesTarget()
         sc.AddMcpServer().WithPrompts(target);
 
         McpServerPrompt prompt = sc.BuildServiceProvider().GetServices<McpServerPrompt>().First(t => t.ProtocolPrompt.Name == "returns_string");
-        var result = await prompt.GetAsync(new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, new JsonRpcRequest { Method = "test", Id = new RequestId("1") })
+        var result = await prompt.GetAsync(new RequestContext<GetPromptRequestParams>(McpServer.Create(new TestServerTransport(), new McpServerOptions()), new JsonRpcRequest { Method = "test", Id = new RequestId("1") })
         {
             Params = new GetPromptRequestParams
             {

tests/ModelContextProtocol.Tests/Configuration/McpServerBuilderExtensionsResourcesTests.cs

@@ -5,7 +5,7 @@
 using ModelContextProtocol.Client;
 using ModelContextProtocol.Protocol;
 using ModelContextProtocol.Server;
-using Moq;
+using ModelContextProtocol.Tests.Utils;
 using System.Collections;
 using System.ComponentModel;
 using System.Threading.Channels;
@@ -345,7 +345,7 @@ public async Task WithResources_TargetInstance_UsesTarget()
         sc.AddMcpServer().WithResources(target);
 
         McpServerResource resource = sc.BuildServiceProvider().GetServices<McpServerResource>().First(t => t.ProtocolResource?.Name == "returns_string");
-        var result = await resource.ReadAsync(new RequestContext<ReadResourceRequestParams>(new Mock<McpServer>().Object, new JsonRpcRequest { Method = "test", Id = new RequestId("1") })
+        var result = await resource.ReadAsync(new RequestContext<ReadResourceRequestParams>(McpServer.Create(new TestServerTransport(), new McpServerOptions()), new JsonRpcRequest { Method = "test", Id = new RequestId("1") })
         {
             Params = new()
             {

tests/ModelContextProtocol.Tests/Configuration/McpServerBuilderExtensionsToolsTests.cs

@@ -5,7 +5,7 @@
 using ModelContextProtocol.Client;
 using ModelContextProtocol.Protocol;
 using ModelContextProtocol.Server;
-using Moq;
+using ModelContextProtocol.Tests.Utils;
 using System.Collections;
 using System.Collections.Concurrent;
 using System.ComponentModel;
@@ -594,7 +594,7 @@ public async Task WithTools_TargetInstance_UsesTarget()
         sc.AddMcpServer().WithTools(target, BuilderToolsJsonContext.Default.Options);
 
         McpServerTool tool = sc.BuildServiceProvider().GetServices<McpServerTool>().First(t => t.ProtocolTool.Name == "get_ctor_parameter");
-        var result = await tool.InvokeAsync(new RequestContext<CallToolRequestParams>(new Mock<McpServer>().Object, new JsonRpcRequest { Method = "test", Id = new RequestId("1") }), TestContext.Current.CancellationToken);
+        var result = await tool.InvokeAsync(new RequestContext<CallToolRequestParams>(McpServer.Create(new TestServerTransport(), new McpServerOptions()), new JsonRpcRequest { Method = "test", Id = new RequestId("1") }), TestContext.Current.CancellationToken);
 
         Assert.Equal(target.GetCtorParameter(), (result.Content[0] as TextContentBlock)?.Text);
     }

tests/ModelContextProtocol.Tests/Server/McpServerPromptTests.cs

@@ -2,7 +2,7 @@
 using Microsoft.Extensions.DependencyInjection;
 using ModelContextProtocol.Protocol;
 using ModelContextProtocol.Server;
-using Moq;
+using ModelContextProtocol.Tests.Utils;
 using System.ComponentModel;
 using System.Reflection;
 using System.Runtime.InteropServices;
@@ -13,6 +13,9 @@ namespace ModelContextProtocol.Tests.Server;
 
 public class McpServerPromptTests
 {
+    private static McpServer CreateTestServer(IServiceProvider? services = null) =>
+        McpServer.Create(new TestServerTransport(), new McpServerOptions(), serviceProvider: services);
+
     private static JsonRpcRequest CreateTestJsonRpcRequest()
     {
         return new JsonRpcRequest
@@ -43,18 +46,18 @@ public void Create_InvalidArgs_Throws()
     [Fact]
     public async Task SupportsMcpServer()
     {
-        Mock<McpServer> mockServer = new();
+        McpServer testServer = CreateTestServer();
 
         McpServerPrompt prompt = McpServerPrompt.Create((McpServer server) =>
         {
-            Assert.Same(mockServer.Object, server);
+            Assert.Same(testServer, server);
             return new ChatMessage(ChatRole.User, "Hello");
         });
 
         Assert.DoesNotContain("server", prompt.ProtocolPrompt.Arguments?.Select(a => a.Name) ?? []);
 
         var result = await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(mockServer.Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(testServer, CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken);
         Assert.NotNull(result);
         Assert.NotNull(result.Messages);
@@ -71,8 +74,7 @@ public async Task SupportsCtorInjection()
         sc.AddSingleton(expectedMyService);
         IServiceProvider services = sc.BuildServiceProvider();
 
-        Mock<McpServer> mockServer = new();
-        mockServer.SetupGet(s => s.Services).Returns(services);
+        McpServer server = CreateTestServer(services);
 
         MethodInfo? testMethod = typeof(HasCtorWithSpecialParameters).GetMethod(nameof(HasCtorWithSpecialParameters.TestPrompt));
         Assert.NotNull(testMethod);
@@ -83,7 +85,7 @@ public async Task SupportsCtorInjection()
         }, new() { Services = services });
 
         var result = await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(mockServer.Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(server, CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken);
         Assert.NotNull(result);
         Assert.NotNull(result.Messages);
@@ -133,11 +135,11 @@ public async Task SupportsServiceFromDI()
         Assert.DoesNotContain("actualMyService", prompt.ProtocolPrompt.Arguments?.Select(a => a.Name) ?? []);
 
         await Assert.ThrowsAnyAsync<ArgumentException>(async () => await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken));
 
         var result = await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()) { Services = services },
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()) { Services = services },
             TestContext.Current.CancellationToken);
         Assert.Equal("Hello", Assert.IsType<TextContentBlock>(result.Messages[0].Content).Text);
     }
@@ -158,7 +160,7 @@ public async Task SupportsOptionalServiceFromDI()
         }, new() { Services = services });
 
         var result = await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken);
         Assert.Equal("Hello", Assert.IsType<TextContentBlock>(result.Messages[0].Content).Text);
     }
@@ -171,7 +173,7 @@ public async Task SupportsDisposingInstantiatedDisposableTargets()
             _ => new DisposablePromptType());
 
         var result = await prompt1.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken);
         Assert.Equal("disposals:1", Assert.IsType<TextContentBlock>(result.Messages[0].Content).Text);
     }
@@ -184,7 +186,7 @@ public async Task SupportsAsyncDisposingInstantiatedAsyncDisposableTargets()
             _ => new AsyncDisposablePromptType());
 
         var result = await prompt1.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken);
         Assert.Equal("asyncDisposals:1", Assert.IsType<TextContentBlock>(result.Messages[0].Content).Text);
     }
@@ -197,7 +199,7 @@ public async Task SupportsAsyncDisposingInstantiatedAsyncDisposableAndDisposable
             _ => new AsyncDisposableAndDisposablePromptType());
 
         var result = await prompt1.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken);
         Assert.Equal("disposals:0, asyncDisposals:1", Assert.IsType<TextContentBlock>(result.Messages[0].Content).Text);
     }
@@ -213,7 +215,7 @@ public async Task CanReturnGetPromptResult()
         });
 
         var actual = await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken);
 
         Assert.Same(expected, actual);
@@ -230,7 +232,7 @@ public async Task CanReturnText()
         });
 
         var actual = await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken);
 
         Assert.NotNull(actual);
@@ -256,7 +258,7 @@ public async Task CanReturnPromptMessage()
         });
 
         var actual = await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken);
 
         Assert.NotNull(actual);
@@ -288,7 +290,7 @@ public async Task CanReturnPromptMessages()
         });
 
         var actual = await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken);
 
         Assert.NotNull(actual);
@@ -315,7 +317,7 @@ public async Task CanReturnChatMessage()
         });
 
         var actual = await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken);
 
         Assert.NotNull(actual);
@@ -347,7 +349,7 @@ public async Task CanReturnChatMessages()
         });
 
         var actual = await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken);
 
         Assert.NotNull(actual);
@@ -368,7 +370,7 @@ public async Task ThrowsForNullReturn()
         });
 
         await Assert.ThrowsAsync<InvalidOperationException>(async () => await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken));
     }
 
@@ -381,7 +383,7 @@ public async Task ThrowsForUnexpectedTypeReturn()
         });
 
         await Assert.ThrowsAsync<InvalidOperationException>(async () => await prompt.GetAsync(
-            new RequestContext<GetPromptRequestParams>(new Mock<McpServer>().Object, CreateTestJsonRpcRequest()),
+            new RequestContext<GetPromptRequestParams>(CreateTestServer(), CreateTestJsonRpcRequest()),
             TestContext.Current.CancellationToken));
     }