Make Hub<T>.Clients settable for testing

- Setting Hub<T>.Clients to null will really set it to its default value

SignalR#3299

Author: halter73

src/Microsoft.AspNet.SignalR.Core/Hub`T.cs

@@ -9,14 +9,21 @@ namespace Microsoft.AspNet.SignalR
     /// </summary>
     public abstract class Hub<T> : Hub where T : class
     {
+        // This allows the typed Client property to be settable for testing
+        private IHubCallerConnectionContext<T> _testClients;
+
         /// <summary>
         /// Gets a dynamic object that represents all clients connected to this hub (not hub instance).
         /// </summary>
         public new IHubCallerConnectionContext<T> Clients
         {
             get
             {
-                return new TypedHubCallerConnectionContext<T>(base.Clients);
+                return _testClients ?? new TypedHubCallerConnectionContext<T>(base.Clients);
+            }
+            set
+            {
+                _testClients = value;
             }
         }
     }

tests/Microsoft.AspNet.SignalR.Tests/Server/Hubs/HubFacts.cs

@@ -134,6 +134,23 @@ public void TypedHubsCanExplicitelyImplementIHub()
             all.VerifyAll();
         }
 
+        [Fact]
+        public void TypedIHubCallerConnectionContextIsSettable()
+        {
+            // https://github.com/SignalR/SignalR/issues/3299
+            var mockClients = new Mock<IHubCallerConnectionContext<IClientContract>>();
+            var all = new Mock<IClientContract>();
+            all.Setup(m => m.send("foo"));
+            mockClients.Setup(m => m.All).Returns(all.Object);
+
+            var hub = new MyTypedIHub();
+            hub.Clients = mockClients.Object;
+            hub.Send("foo");
+
+            mockClients.VerifyAll();
+            all.VerifyAll();
+        }
+
         private class MyTestableHub : Hub
         {
             public void Send(string messages)