test(batch7): implement t3 cross-cutting mapped tests

dotnet/tests/ZB.MOM.NatsNet.Server.Tests/ImplBacklog/ConfigReloaderTests.cs

@@ -1,5 +1,9 @@
+using System.Text;
 using Shouldly;
 using ZB.MOM.NatsNet.Server;
+using ZB.MOM.NatsNet.Server.Auth;
+using ZB.MOM.NatsNet.Server.Internal;
+using ZB.MOM.NatsNet.Server.Internal.DataStructures;
 
 namespace ZB.MOM.NatsNet.Server.Tests.ImplBacklog;
 
@@ -148,4 +152,51 @@ public sealed class ConfigReloaderTests
             ServerOptions.NoErrOnUnknownFields(false);
         }
     }
+
+    [Fact] // T:2774
+    public void ConfigReloadAuthDoesNotBreakRouteInterest_ShouldSucceed()
+    {
+        var (server, createError) = NatsServer.NewServer(new ServerOptions
+        {
+            NoLog = true,
+            NoSigs = true,
+            Accounts = [new Account { Name = "A" }],
+            Users = [new User
+            {
+                Username = "u",
+                Password = "p",
+                Account = new Account { Name = "A" },
+            }],
+        });
+
+        createError.ShouldBeNull();
+        server.ShouldNotBeNull();
+
+        try
+        {
+            var (account, lookupError) = server!.LookupAccount("A");
+            lookupError.ShouldBeNull();
+            account.ShouldNotBeNull();
+
+            account!.Sublist = SubscriptionIndex.NewSublistWithCache();
+            var insertError = account.Sublist.Insert(new Subscription
+            {
+                Subject = Encoding.ASCII.GetBytes("foo"),
+                Queue = Encoding.ASCII.GetBytes("bar"),
+            });
+            insertError.ShouldBeNull();
+            account.TotalSubs().ShouldBe(1);
+
+            server.ReloadAuthorization();
+
+            var (updatedAccount, updatedLookupError) = server.LookupAccount("A");
+            updatedLookupError.ShouldBeNull();
+            updatedAccount.ShouldNotBeNull();
+            updatedAccount!.TotalSubs().ShouldBe(1);
+        }
+        finally
+        {
+            server!.Shutdown();
+        }
+    }
 }