Automatically fall back from Streamable HTTP to SSE on the client by default (#456)

tests/ModelContextProtocol.AspNetCore.Tests/MapMcpStreamableHttpTests.cs

@@ -1,5 +1,6 @@
 using Microsoft.AspNetCore.Builder;
 using Microsoft.Extensions.DependencyInjection;
+using ModelContextProtocol.Client;
 
 namespace ModelContextProtocol.AspNetCore.Tests;
 
@@ -34,4 +35,112 @@ public class MapMcpStreamableHttpTests(ITestOutputHelper outputHelper) : MapMcpT
 
         Assert.Equal("TestCustomRouteServer", mcpClient.ServerInfo.Name);
     }
+
+    [Fact]
+    public async Task StreamableHttpMode_Works_WithRootEndpoint()
+    {
+        Builder.Services.AddMcpServer(options =>
+        {
+            options.ServerInfo = new()
+            {
+                Name = "StreamableHttpTestServer",
+                Version = "1.0.0",
+            };
+        }).WithHttpTransport(ConfigureStateless);
+        await using var app = Builder.Build();
+
+        app.MapMcp();
+
+        await app.StartAsync(TestContext.Current.CancellationToken);
+
+        await using var mcpClient = await ConnectAsync("/", new()
+        {
+            Endpoint = new Uri("http://localhost/"),
+            TransportMode = HttpTransportMode.AutoDetect
+        });
+
+        Assert.Equal("StreamableHttpTestServer", mcpClient.ServerInfo.Name);
+    }
+
+    [Fact]
+    public async Task AutoDetectMode_Works_WithRootEndpoint()
+    {
+        Builder.Services.AddMcpServer(options =>
+        {
+            options.ServerInfo = new()
+            {
+                Name = "AutoDetectTestServer",
+                Version = "1.0.0",
+            };
+        }).WithHttpTransport(ConfigureStateless);
+        await using var app = Builder.Build();
+
+        app.MapMcp();
+
+        await app.StartAsync(TestContext.Current.CancellationToken);
+
+        await using var mcpClient = await ConnectAsync("/", new()
+        {
+            Endpoint = new Uri("http://localhost/"),
+            TransportMode = HttpTransportMode.AutoDetect
+        });
+
+        Assert.Equal("AutoDetectTestServer", mcpClient.ServerInfo.Name);
+    }
+
+    [Fact]
+    public async Task AutoDetectMode_Works_WithSseEndpoint()
+    {
+        Assert.SkipWhen(Stateless, "SSE endpoint is disabled in stateless mode.");
+
+        Builder.Services.AddMcpServer(options =>
+        {
+            options.ServerInfo = new()
+            {
+                Name = "AutoDetectSseTestServer",
+                Version = "1.0.0",
+            };
+        }).WithHttpTransport(ConfigureStateless);
+        await using var app = Builder.Build();
+
+        app.MapMcp();
+
+        await app.StartAsync(TestContext.Current.CancellationToken);
+
+        await using var mcpClient = await ConnectAsync("/sse", new()
+        {
+            Endpoint = new Uri("http://localhost/sse"),
+            TransportMode = HttpTransportMode.AutoDetect
+        });
+
+        Assert.Equal("AutoDetectSseTestServer", mcpClient.ServerInfo.Name);
+    }
+
+    [Fact]
+    public async Task SseMode_Works_WithSseEndpoint()
+    {
+        Assert.SkipWhen(Stateless, "SSE endpoint is disabled in stateless mode.");
+
+        Builder.Services.AddMcpServer(options =>
+        {
+            options.ServerInfo = new()
+            {
+                Name = "SseTestServer",
+                Version = "1.0.0",
+            };
+        }).WithHttpTransport(ConfigureStateless);
+        await using var app = Builder.Build();
+
+        app.MapMcp();
+
+        await app.StartAsync(TestContext.Current.CancellationToken);
+
+        await using var mcpClient = await ConnectAsync(options: new()
+        {
+            Endpoint = new Uri("http://localhost/sse"),
+            TransportMode = HttpTransportMode.Sse
+        });
+
+        Assert.Equal("SseTestServer", mcpClient.ServerInfo.Name);
+    }
 }