save checkpoint

src/Router/__Tests/StellaOps.Router.Gateway.Tests/RateLimit/RateLimitServiceCollectionExtensionsTests.cs

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+using FluentAssertions;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using StellaOps.Router.Gateway.RateLimit;
+using Xunit;
+
+namespace StellaOps.Router.Gateway.Tests.RateLimit;
+
+[Trait("Category", "Unit")]
+public sealed class RateLimitServiceCollectionExtensionsTests
+{
+    [Fact]
+    public void AddRouterRateLimiting_WithoutRules_RegistersNoOpRateLimitService()
+    {
+        var configuration = new ConfigurationBuilder()
+            .AddInMemoryCollection(new Dictionary<string, string?>())
+            .Build();
+
+        var services = new ServiceCollection();
+        services.AddLogging();
+
+        services.AddRouterRateLimiting(configuration);
+
+        using var provider = services.BuildServiceProvider();
+
+        provider.GetService<RateLimitService>().Should().NotBeNull();
+        provider.GetService<InstanceRateLimiter>().Should().BeNull();
+        provider.GetService<EnvironmentRateLimiter>().Should().BeNull();
+    }
+}