svrnty-mcp-gateway/tests/Svrnty.MCP.Gateway.AspNetCore.Tests/Middleware/GatewayMiddlewareTests.cs

using Xunit;
using Moq;
using Microsoft.AspNetCore.Http;
using Svrnty.MCP.Gateway.AspNetCore.Middleware;
using Svrnty.MCP.Gateway.Core.Interfaces;
using Svrnty.MCP.Gateway.Core.Models;
using System.Text;
using System.Text.Json;

namespace Svrnty.MCP.Gateway.AspNetCore.Tests.Middleware;

/// <summary>
/// Unit tests for GatewayMiddleware following TDD approach.
/// Tests HTTP request interception and gateway routing.
/// </summary>
public class GatewayMiddlewareTests
{
    [Fact]
    public async Task InvokeAsync_WithGatewayRequest_RoutesToGateway()
    {
        // Arrange
        var mockRouter = new Mock<IGatewayRouter>();
        mockRouter.Setup(r => r.RouteAsync(It.IsAny<GatewayRequest>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new GatewayResponse { Success = true, Result = new Dictionary<string, object> { ["data"] = "test" } });

        var middleware = new GatewayMiddleware(
            next: (HttpContext _) => Task.CompletedTask,
            router: mockRouter.Object
        );

        var context = new DefaultHttpContext();
        context.Request.Method = "POST";
        context.Request.Path = "/mcp/invoke";
        context.Request.ContentType = "application/json";

        var requestBody = JsonSerializer.Serialize(new { toolName = "test_tool", arguments = new { } });
        context.Request.Body = new MemoryStream(Encoding.UTF8.GetBytes(requestBody));
        context.Response.Body = new MemoryStream();

        // Act
        await middleware.InvokeAsync(context);

        // Assert
        mockRouter.Verify(r => r.RouteAsync(It.Is<GatewayRequest>(req => req.ToolName == "test_tool"), It.IsAny<CancellationToken>()), Times.Once);
        Assert.Equal(200, context.Response.StatusCode);
    }

    [Fact]
    public async Task InvokeAsync_WithNonGatewayPath_CallsNext()
    {
        // Arrange
        var mockRouter = new Mock<IGatewayRouter>();
        var nextCalled = false;

        var middleware = new GatewayMiddleware(
            next: (HttpContext _) => { nextCalled = true; return Task.CompletedTask; },
            router: mockRouter.Object
        );

        var context = new DefaultHttpContext();
        context.Request.Method = "GET";
        context.Request.Path = "/api/other";

        // Act
        await middleware.InvokeAsync(context);

        // Assert
        Assert.True(nextCalled);
        mockRouter.Verify(r => r.RouteAsync(It.IsAny<GatewayRequest>(), It.IsAny<CancellationToken>()), Times.Never);
    }

    [Fact]
    public async Task InvokeAsync_WithGatewayError_Returns500()
    {
        // Arrange
        var mockRouter = new Mock<IGatewayRouter>();
        mockRouter.Setup(r => r.RouteAsync(It.IsAny<GatewayRequest>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new GatewayResponse { Success = false, Error = "Routing failed", ErrorCode = "ROUTE_ERROR" });

        var middleware = new GatewayMiddleware(
            next: (HttpContext _) => Task.CompletedTask,
            router: mockRouter.Object
        );

        var context = new DefaultHttpContext();
        context.Request.Method = "POST";
        context.Request.Path = "/mcp/invoke";
        context.Request.ContentType = "application/json";

        var requestBody = JsonSerializer.Serialize(new { toolName = "test_tool" });
        context.Request.Body = new MemoryStream(Encoding.UTF8.GetBytes(requestBody));
        context.Response.Body = new MemoryStream();

        // Act
        await middleware.InvokeAsync(context);

        // Assert
        Assert.Equal(500, context.Response.StatusCode);
    }

    [Fact]
    public async Task InvokeAsync_WithInvalidJson_Returns400()
    {
        // Arrange
        var mockRouter = new Mock<IGatewayRouter>();
        var middleware = new GatewayMiddleware(
            next: (HttpContext _) => Task.CompletedTask,
            router: mockRouter.Object
        );

        var context = new DefaultHttpContext();
        context.Request.Method = "POST";
        context.Request.Path = "/mcp/invoke";
        context.Request.ContentType = "application/json";
        context.Request.Body = new MemoryStream(Encoding.UTF8.GetBytes("invalid json"));
        context.Response.Body = new MemoryStream();

        // Act
        await middleware.InvokeAsync(context);

        // Assert
        Assert.Equal(400, context.Response.StatusCode);
    }

    [Fact]
    public async Task InvokeAsync_ExtractsClientIdFromHeader()
    {
        // Arrange
        var mockRouter = new Mock<IGatewayRouter>();
        mockRouter.Setup(r => r.RouteAsync(It.IsAny<GatewayRequest>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new GatewayResponse { Success = true });

        var middleware = new GatewayMiddleware(
            next: (HttpContext _) => Task.CompletedTask,
            router: mockRouter.Object
        );

        var context = new DefaultHttpContext();
        context.Request.Method = "POST";
        context.Request.Path = "/mcp/invoke";
        context.Request.ContentType = "application/json";
        context.Request.Headers["X-Client-Id"] = "test-client";

        var requestBody = JsonSerializer.Serialize(new { toolName = "test_tool" });
        context.Request.Body = new MemoryStream(Encoding.UTF8.GetBytes(requestBody));
        context.Response.Body = new MemoryStream();

        // Act
        await middleware.InvokeAsync(context);

        // Assert
        mockRouter.Verify(r => r.RouteAsync(
            It.Is<GatewayRequest>(req => req.ClientId == "test-client"),
            It.IsAny<CancellationToken>()), Times.Once);
    }

    [Fact]
    public async Task InvokeAsync_ReturnsJsonResponse()
    {
        // Arrange
        var mockRouter = new Mock<IGatewayRouter>();
        var expectedResult = new Dictionary<string, object> { ["status"] = "success", ["value"] = 42 };
        mockRouter.Setup(r => r.RouteAsync(It.IsAny<GatewayRequest>(), It.IsAny<CancellationToken>()))
            .ReturnsAsync(new GatewayResponse { Success = true, Result = expectedResult });

        var middleware = new GatewayMiddleware(
            next: (HttpContext _) => Task.CompletedTask,
            router: mockRouter.Object
        );

        var context = new DefaultHttpContext();
        context.Request.Method = "POST";
        context.Request.Path = "/mcp/invoke";
        context.Request.ContentType = "application/json";

        var requestBody = JsonSerializer.Serialize(new { toolName = "test_tool" });
        context.Request.Body = new MemoryStream(Encoding.UTF8.GetBytes(requestBody));
        context.Response.Body = new MemoryStream();

        // Act
        await middleware.InvokeAsync(context);

        // Assert
        Assert.Equal("application/json", context.Response.ContentType);

        context.Response.Body.Seek(0, SeekOrigin.Begin);
        var responseBody = await new StreamReader(context.Response.Body).ReadToEndAsync();
        Assert.Contains("success", responseBody);
        Assert.Contains("42", responseBody);
    }
}