Add round-trip integration tests for MCP Apps _meta.ui serialization

tests/ModelContextProtocol.Tests/Server/McpAppsIntegrationTests.cs

@@ -0,0 +1,100 @@
+#pragma warning disable MCPEXP003
+
+using Microsoft.Extensions.DependencyInjection;
+using ModelContextProtocol.Client;
+using ModelContextProtocol.Extensions.Apps;
+using ModelContextProtocol.Server;
+using System.ComponentModel;
+using System.Text.Json.Nodes;
+
+namespace ModelContextProtocol.Tests.Server;
+
+/// <summary>
+/// Round-trip integration tests for the MCP Apps <c>_meta.ui</c> metadata: tools registered
+/// with <see cref="McpAppUiAttribute"/> and processed by <c>WithMcpApps()</c> are listed through
+/// <see cref="McpClient.ListToolsAsync"/> and the structured <c>_meta.ui</c> object is verified
+/// after serializing across the client-server transport.
+/// </summary>
+public class McpAppsIntegrationTests : ClientServerTestBase
+{
+    public McpAppsIntegrationTests(ITestOutputHelper testOutputHelper)
+        : base(testOutputHelper)
+    {
+    }
+
+    protected override void ConfigureServices(ServiceCollection services, IMcpServerBuilder mcpServerBuilder)
+    {
+        mcpServerBuilder
+            .WithTools<AppUiTools>()
+            .WithMcpApps();
+    }
+
+    [Fact]
+    public async Task ListToolsAsync_RoundTripsMetaUi_ForToolWithAppUiAttribute()
+    {
+        await using McpClient client = await CreateMcpClientForServer();
+
+        var tools = await client.ListToolsAsync(cancellationToken: TestContext.Current.CancellationToken);
+
+        var weatherTool = Assert.Single(tools, t => t.Name == "weather_tool");
+
+        JsonObject? uiNode = weatherTool.ProtocolTool.Meta?["ui"]?.AsObject();
+        Assert.NotNull(uiNode);
+        Assert.Equal("ui://weather/view.html", uiNode["resourceUri"]?.GetValue<string>());
+
+        // Visibility was not restricted, so the property must be absent entirely
+        // (not merely serialized as null).
+        Assert.False(uiNode.ContainsKey("visibility"));
+    }
+
+    [Fact]
+    public async Task ListToolsAsync_RoundTripsMetaUiVisibility_ForRestrictedTool()
+    {
+        await using McpClient client = await CreateMcpClientForServer();
+
+        var tools = await client.ListToolsAsync(cancellationToken: TestContext.Current.CancellationToken);
+
+        var modelOnlyTool = Assert.Single(tools, t => t.Name == "model_only_tool");
+
+        JsonObject? uiNode = modelOnlyTool.ProtocolTool.Meta?["ui"]?.AsObject();
+        Assert.NotNull(uiNode);
+        Assert.Equal("ui://model-only/view.html", uiNode["resourceUri"]?.GetValue<string>());
+
+        JsonArray? visibility = uiNode["visibility"]?.AsArray();
+        Assert.NotNull(visibility);
+        JsonNode? single = Assert.Single(visibility);
+        Assert.Equal(McpUiToolVisibility.Model, single?.GetValue<string>());
+    }
+
+    [Fact]
+    public async Task ListToolsAsync_HasNoUiMeta_ForToolWithoutAppUiAttribute()
+    {
+        await using McpClient client = await CreateMcpClientForServer();
+
+        var tools = await client.ListToolsAsync(cancellationToken: TestContext.Current.CancellationToken);
+
+        var plainTool = Assert.Single(tools, t => t.Name == "plain_tool");
+
+        // The tool must carry no "ui" metadata at all: either no _meta object,
+        // or a _meta without the "ui" key (not a "ui": null entry).
+        JsonObject? meta = plainTool.ProtocolTool.Meta;
+        Assert.False(meta is not null && meta.ContainsKey("ui"));
+    }
+
+    public sealed class AppUiTools
+    {
+        [McpServerTool(Name = "weather_tool")]
+        [McpAppUi(ResourceUri = "ui://weather/view.html")]
+        [Description("Get weather")]
+        public static string WeatherTool(string location) => $"Weather for {location}";
+
+        [McpServerTool(Name = "model_only_tool")]
+        [McpAppUi(ResourceUri = "ui://model-only/view.html", Visibility = [McpUiToolVisibility.Model])]
+        [Description("Model only")]
+        public static string ModelOnlyTool(string location) => $"Model only for {location}";
+
+        [McpServerTool(Name = "plain_tool")]
+        [Description("Plain tool without app UI")]
+        public static string PlainTool(string input) => input;
+    }
+}