Fix router frontdoor readiness and route contracts

src/Router/__Tests/StellaOps.Gateway.WebService.Tests/Integration/GatewayIntegrationTests.cs

@@ -1,9 +1,10 @@
 using System.Net;
+using System.Text.Json;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Mvc.Testing;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.Options;
+using StellaOps.Gateway.WebService.Configuration;
 using StellaOps.Gateway.WebService.Routing;
 using StellaOps.Router.Common.Abstractions;
 using StellaOps.Router.Common.Enums;
@@ -51,6 +52,93 @@ public sealed class GatewayIntegrationTests : IClassFixture<GatewayWebApplicatio
         Assert.Equal(HttpStatusCode.OK, response.StatusCode);
     }
 
+    [Fact]
+    public async Task HealthReady_ReturnsServiceUnavailable_WhenRequiredMicroserviceIsMissing()
+    {
+        using var factory = CreateFactoryWithRequiredServices("policy");
+        var client = factory.CreateClient();
+
+        var response = await client.GetAsync("/health/ready");
+
+        Assert.Equal(HttpStatusCode.ServiceUnavailable, response.StatusCode);
+
+        using var payload = JsonDocument.Parse(await response.Content.ReadAsStringAsync());
+        Assert.Equal("policy", payload.RootElement.GetProperty("missingMicroservices")[0].GetString());
+    }
+
+    [Fact]
+    public async Task HealthReady_ReturnsOk_WhenRequiredMicroserviceIsRegistered()
+    {
+        using var factory = CreateFactoryWithRequiredServices("policy");
+        using (var scope = factory.Services.CreateScope())
+        {
+            var routingState = scope.ServiceProvider.GetRequiredService<IGlobalRoutingState>();
+            routingState.AddConnection(new ConnectionState
+            {
+                ConnectionId = "conn-policy",
+                Instance = new InstanceDescriptor
+                {
+                    InstanceId = "policy-01",
+                    ServiceName = "policy-gateway",
+                    Version = "1.0.0",
+                    Region = "test"
+                },
+                Status = InstanceHealthStatus.Healthy,
+                TransportType = TransportType.Messaging
+            });
+        }
+
+        var client = factory.CreateClient();
+        var response = await client.GetAsync("/health/ready");
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task HealthReady_ReturnsServiceUnavailable_WhenOnlySiblingServiceIsRegistered()
+    {
+        using var factory = CreateFactoryWithRequiredServices("policy");
+        using (var scope = factory.Services.CreateScope())
+        {
+            var routingState = scope.ServiceProvider.GetRequiredService<IGlobalRoutingState>();
+            routingState.AddConnection(new ConnectionState
+            {
+                ConnectionId = "conn-policy-engine",
+                Instance = new InstanceDescriptor
+                {
+                    InstanceId = "policy-engine-01",
+                    ServiceName = "policy-engine",
+                    Version = "1.0.0",
+                    Region = "test"
+                },
+                Status = InstanceHealthStatus.Healthy,
+                TransportType = TransportType.Messaging
+            });
+        }
+
+        var client = factory.CreateClient();
+        var response = await client.GetAsync("/health/ready");
+
+        Assert.Equal(HttpStatusCode.ServiceUnavailable, response.StatusCode);
+
+        using var payload = JsonDocument.Parse(await response.Content.ReadAsStringAsync());
+        Assert.Equal("policy", payload.RootElement.GetProperty("missingMicroservices")[0].GetString());
+    }
+
+    private WebApplicationFactory<Program> CreateFactoryWithRequiredServices(params string[] requiredServices)
+    {
+        return new GatewayWebApplicationFactory().WithWebHostBuilder(builder =>
+        {
+            builder.ConfigureTestServices(services =>
+            {
+                services.PostConfigure<GatewayOptions>(options =>
+                {
+                    options.Health.RequiredMicroservices = requiredServices.ToList();
+                });
+            });
+        });
+    }
+
     [Fact]
     public async Task OpenApiJson_ReturnsValidOpenApiDocument()
     {