fix(external-system-gateway): resolve ExternalSystemGateway-012,013,014 — failure logging, connection-limit wiring, test coverage; ExternalSystemGateway-011 flagged

tests/ScadaLink.ExternalSystemGateway.Tests/ServiceWiringTests.cs

@@ -0,0 +1,52 @@
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Http;
+using NSubstitute;
+using ScadaLink.Commons.Interfaces.Repositories;
+
+namespace ScadaLink.ExternalSystemGateway.Tests;
+
+/// <summary>
+/// ExternalSystemGateway-013: configuration options must actually influence the
+/// registered HTTP client — an operator setting them must not be silently ignored.
+/// </summary>
+public class ServiceWiringTests
+{
+    [Fact]
+    public void MaxConcurrentConnectionsPerSystem_IsAppliedToTheNamedHttpClientPrimaryHandler()
+    {
+        var config = new ConfigurationBuilder()
+            .AddInMemoryCollection(new Dictionary<string, string?>
+            {
+                ["ScadaLink:ExternalSystemGateway:MaxConcurrentConnectionsPerSystem"] = "4",
+            })
+            .Build();
+
+        var services = new ServiceCollection();
+        services.AddLogging();
+        services.AddSingleton<IConfiguration>(config);
+        services.AddSingleton(Substitute.For<IExternalSystemRepository>());
+        services.AddExternalSystemGateway();
+
+        using var provider = services.BuildServiceProvider();
+
+        // Resolve the per-system named client's message-handler chain and walk to the
+        // primary handler — the option must be reflected in MaxConnectionsPerServer.
+        var handlerFactory = provider.GetRequiredService<IHttpMessageHandlerFactory>();
+        var handler = handlerFactory.CreateHandler("ExternalSystem_AnySystem");
+
+        var primary = FindPrimaryHandler(handler);
+        var sockets = Assert.IsType<SocketsHttpHandler>(primary);
+        Assert.Equal(4, sockets.MaxConnectionsPerServer);
+    }
+
+    private static HttpMessageHandler FindPrimaryHandler(HttpMessageHandler handler)
+    {
+        var current = handler;
+        while (current is DelegatingHandler delegating && delegating.InnerHandler != null)
+        {
+            current = delegating.InnerHandler;
+        }
+        return current;
+    }
+}