Add tests for ClientWebSocket connections thru a proxy (#28031)

Created new tests for verifying ClientWebSocket connections
end-to-end thru a proxy.

Opened new issues #28024 and #28027 which cause the new tests to fail.

Fixes #26957

Author: davidsh

src/Common/tests/System/Net/Configuration.WebSockets.cs

@@ -8,6 +8,8 @@ public static partial class Configuration
     {
         public static partial class WebSockets
         {
+            public static string ProxyServerUri => GetValue("COREFX_WEBSOCKETPROXYSERVERURI");
+
             public static string Host => GetValue("COREFX_WEBSOCKETHOST", DefaultAzureServer);
 
             public static string SecureHost => GetValue("COREFX_SECUREWEBSOCKETHOST", DefaultAzureServer);

src/System.Net.WebSockets.Client/tests/ClientWebSocketOptionsTests.cs

@@ -51,7 +51,7 @@ public static void Proxy_Roundtrips()
 
         [OuterLoop] // TODO: Issue #11345
         [ConditionalTheory(nameof(WebSocketsSupported)), MemberData(nameof(EchoServers))]
-        public async Task NullProxySet_ConnectsSuccessfully(Uri server)
+        public async Task Proxy_SetNull_ConnectsSuccessfully(Uri server)
         {
             for (int i = 0; i < 3; i++) // Connect and disconnect multiple times to exercise shared handler on netcoreapp
             {
@@ -67,6 +67,43 @@ public async Task NullProxySet_ConnectsSuccessfully(Uri server)
             }
         }
 
+        [ActiveIssue(28027)]
+        [OuterLoop] // TODO: Issue #11345
+        [ConditionalTheory(nameof(WebSocketsSupported)), MemberData(nameof(EchoServers))]
+        public async Task Proxy_ConnectThruProxy_Success(Uri server)
+        {
+            string proxyServerUri = System.Net.Test.Common.Configuration.WebSockets.ProxyServerUri;
+            if (string.IsNullOrEmpty(proxyServerUri))
+            {
+                _output.WriteLine("Skipping test...no proxy server defined.");
+                return;
+            }
+            
+            _output.WriteLine($"ProxyServer: {proxyServerUri}");
+            
+            IWebProxy proxy = new WebProxy(new Uri(proxyServerUri));
+            using (ClientWebSocket cws = await WebSocketHelper.GetConnectedWebSocket(
+                server,
+                TimeOutMilliseconds,
+                _output,
+                default(TimeSpan),
+                proxy))
+            {
+                var cts = new CancellationTokenSource(TimeOutMilliseconds);
+                Assert.Equal(WebSocketState.Open, cws.State);
+
+                var closeStatus = WebSocketCloseStatus.NormalClosure;
+                string closeDescription = "Normal Closure";
+
+                await cws.CloseAsync(closeStatus, closeDescription, cts.Token);
+
+                // Verify a clean close frame handshake.
+                Assert.Equal(WebSocketState.Closed, cws.State);
+                Assert.Equal(closeStatus, cws.CloseStatus);
+                Assert.Equal(closeDescription, cws.CloseStatusDescription);
+            }
+        }
+
         [ConditionalFact(nameof(WebSocketsSupported))]
         public static void SetBuffer_InvalidArgs_Throws()
         {

src/System.Net.WebSockets.Client/tests/WebSocketHelper.cs

@@ -65,10 +65,16 @@ public static Task<ClientWebSocket> GetConnectedWebSocket(
             Uri server,
             int timeOutMilliseconds,
             ITestOutputHelper output,
-            TimeSpan keepAliveInterval = default) =>
+            TimeSpan keepAliveInterval = default,
+            IWebProxy proxy = null) =>
             Retry(output, async () =>
             {
                 var cws = new ClientWebSocket();
+                if (proxy != null)
+                {
+                    cws.Options.Proxy = proxy;
+                }
+                
                 if (keepAliveInterval.TotalSeconds > 0)
                 {
                     cws.Options.KeepAliveInterval = keepAliveInterval;