[ECO-5646] Added test to make sure non-recoverable errors are always retried

on primary host first

Author: sacOO7

src/IO.Ably.Tests.Shared/Realtime/ConnectionSpecs/ConnectionFallbackSpecs.cs

@@ -7,6 +7,7 @@
 using FluentAssertions;
 using IO.Ably.Realtime;
 using IO.Ably.Realtime.Workflow;
+using IO.Ably.Tests.Infrastructure;
 using IO.Ably.Types;
 using Xunit;
 using Xunit.Abstractions;
@@ -342,6 +343,55 @@ public async Task WhenItMovesFromDisconnectedToSuspended_ShouldTryDefaultHostAga
             realtimeHosts.Last().Should().Be("realtime.ably.io");
         }
 
+        [Fact]
+        [Trait("spec", "RTN17j")]
+        [Trait("spec", "RTN17f")]
+        public async Task WhenConnectionRetryNonRecoverableError_ShouldAlwaysTryDefaultHostFirst()
+        {
+            var client = await GetConnectedClient(opts =>
+            {
+                opts.DisconnectedRetryTimeout = TimeSpan.FromSeconds(2);
+                opts.SuspendedRetryTimeout = TimeSpan.FromSeconds(2);
+            });
+
+            // Reduced connectionStateTTL for limited disconnected retries upto 20 seconds
+            client.State.Connection.ConnectionStateTtl = TimeSpan.FromSeconds(20);
+
+            var realtimeHosts = new List<string>();
+            FakeTransportFactory.InitialiseFakeTransport = p => realtimeHosts.Add(p.Parameters.Host);
+
+            client.Connection.On(ConnectionEvent.Connecting, stateChange =>
+            {
+                if (stateChange.Previous == ConnectionState.Disconnected)
+                {
+                    ReceiveNonRecoverableDisconnectMessage(client);
+                }
+            });
+
+            // Receive first disconnect message on CONNECTED client, will call above callback after timeout
+            ReceiveNonRecoverableDisconnectMessage(client);
+
+            await new ConditionalAwaiter(() => client.Connection.State == ConnectionState.Suspended, null, 120);
+
+            client.Connection.State.Should().Be(ConnectionState.Suspended);
+            await client.WaitForState(ConnectionState.Connecting);
+
+            ReceiveNonRecoverableDisconnectMessage(client);
+
+            await client.WaitForState(ConnectionState.Suspended);
+            await client.WaitForState(ConnectionState.Connecting);
+
+            realtimeHosts.Should().AllBe("realtime.ably.io");
+        }
+
+        private void ReceiveNonRecoverableDisconnectMessage(AblyRealtime client)
+        {
+            client.FakeProtocolMessageReceived(new ProtocolMessage(ProtocolMessage.MessageAction.Disconnected)
+            {
+                Error = new ErrorInfo { StatusCode = HttpStatusCode.Forbidden }
+            });
+        }
+
         public ConnectionFallbackSpecs(ITestOutputHelper output)
             : base(output)
         {