Tests to validate #686

This adds IPv4 parsing and connect testing, verified that the fix in #686 will work.

StackExchange.Redis.Tests/ConnectByIP.cs

+using System.Net.Sockets;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace StackExchange.Redis.Tests
+{
+    public class ConnectByIP : TestBase
+    {
+        public ConnectByIP(ITestOutputHelper output) : base (output) { }
+
+        [Fact]
+        public void ParseEndpoints()
+        {
+            var eps = new EndPointCollection
+            {
+                { "127.0.0.1", 1000 },
+                { "::1", 1001 }
+            };
+
+            Assert.Equal(AddressFamily.InterNetwork, eps[0].AddressFamily);
+            Assert.Equal(AddressFamily.InterNetworkV6, eps[1].AddressFamily);
+
+            Assert.Equal("127.0.0.1:1000", eps[0].ToString());
+            Assert.Equal("[::1]:1001", eps[1].ToString());
+        }
+
+        [Fact]
+        public void IPv4Connection()
+        {
+            var config = new ConfigurationOptions
+            {
+                EndPoints = { { TestConfig.Current.IPv4Server, TestConfig.Current.IPv4Port } }
+            };
+            using (var conn = ConnectionMultiplexer.Connect(config))
+            {
+                var server = conn.GetServer(config.EndPoints[0]);
+                Assert.Equal(AddressFamily.InterNetwork, server.EndPoint.AddressFamily);
+                server.Ping();
+            }
+        }
+
+        [Fact]
+        public void IPv6Connection()
+        {
+            var config = new ConfigurationOptions
+            {
+                EndPoints = { { TestConfig.Current.IPv6Server, TestConfig.Current.IPv6Port } }
+            };
+            using (var conn = ConnectionMultiplexer.Connect(config))
+            {
+                var server = conn.GetServer(config.EndPoints[0]);
+                Assert.Equal(AddressFamily.InterNetworkV6, server.EndPoint.AddressFamily);
+                server.Ping();
+            }
+        }
+    }
+}

StackExchange.Redis.Tests/Helpers/TestConfig.cs

@@ -50,6 +50,11 @@ public class Config
             public int SecurePort { get; set; } = 6381;
             public string SecurePassword { get; set; } = "changeme";
 
+            public string IPv4Server { get; set; } = "127.0.0.1";
+            public int IPv4Port { get; set; } = 6379;
+            public string IPv6Server { get; set; } = "::1";
+            public int IPv6Port { get; set; } = 6379;
+
             public string RemoteServer { get; set; } = "127.0.0.1";
             public int RemotePort { get; set; } = 6379;