CSHARP-1720: Code review changes.

Author: rstam

src/MongoDB.Driver.Core/Core/Clusters/ServerSelectors/ReadPreferenceServerSelector.cs

@@ -137,7 +137,7 @@ private IEnumerable<ServerDescription> SelectForReplicaSet(ClusterDescription cl
                 var minHeartBeatIntervalTicks = servers.Select(s => s.HeartbeatInterval.Ticks).Min();
                 if (_maxStaleness.Value.Ticks < 2 * minHeartBeatIntervalTicks)
                 {
-                    throw new MongoClientException("MaxStaleness must be at least twice the heartbeat frequency.");
+                    throw new MongoClientException("MaxStaleness must be at least twice the heartbeat interval.");
                 }
 
                 servers = new CachedEnumerable<ServerDescription>(SelectFreshServers(cluster, servers)); // prevent multiple enumeration

src/MongoDB.Driver/MongoUrlBuilder.cs

@@ -256,7 +256,7 @@ public TimeSpan HeartbeatTimeout
             {
                 if (value < TimeSpan.Zero && value != Timeout.InfiniteTimeSpan)
                 {
-                    throw new ArgumentOutOfRangeException("value", "HeartbeatInterval must be greater than or equal to zero.");
+                    throw new ArgumentOutOfRangeException("value", "HeartbeatTimeout must be greater than or equal to zero.");
                 }
                 _heartbeatTimeout = value;
             }

tests/MongoDB.Driver.Core.Tests/Core/Configuration/ConnectionStringTests.cs

@@ -342,6 +342,12 @@ public void When_gssapiServiceName_is_specified(string connectionString, string
         [InlineData("mongodb://localhost?heartbeatInterval=15s", 1000 * 15)]
         [InlineData("mongodb://localhost?heartbeatInterval=15m", 1000 * 60 * 15)]
         [InlineData("mongodb://localhost?heartbeatInterval=15h", 1000 * 60 * 60 * 15)]
+        [InlineData("mongodb://localhost?heartbeatFrequency=15ms", 15)]
+        [InlineData("mongodb://localhost?heartbeatFrequencyMS=15", 15)]
+        [InlineData("mongodb://localhost?heartbeatFrequency=15", 1000 * 15)]
+        [InlineData("mongodb://localhost?heartbeatFrequency=15s", 1000 * 15)]
+        [InlineData("mongodb://localhost?heartbeatFrequency=15m", 1000 * 60 * 15)]
+        [InlineData("mongodb://localhost?heartbeatFrequency=15h", 1000 * 60 * 60 * 15)]
         public void When_heartbeat_interval_is_specified(string connectionString, int milliseconds)
         {
             var subject = new ConnectionString(connectionString);

tests/MongoDB.Driver.Core.Tests/Core/Configuration/ServerSettingsTests.cs

@@ -21,7 +21,21 @@ namespace MongoDB.Driver.Core.Configuration
 {
     public class ServerSettingsTests
     {
-        private static readonly ServerSettings __defaults = new ServerSettings();
+        [Fact]
+        public void DefaultHeartbeatInterval_should_return_expected_result()
+        {
+            var result = ServerSettings.DefaultHeartbeatInterval;
+
+            result.Should().Be(TimeSpan.FromSeconds(10));
+        }
+
+        [Fact]
+        public void DefaultHeartbeatTimeout_should_return_expected_result()
+        {
+            var result = ServerSettings.DefaultHeartbeatTimeout;
+
+            result.Should().Be(TimeSpan.FromSeconds(10));
+        }
 
         [Fact]
         public void constructor_should_initialize_instance()
@@ -56,7 +70,7 @@ public void constructor_with_heartbeatInterval_should_initialize_instance()
             var subject = new ServerSettings(heartbeatInterval: heartbeatInterval);
 
             subject.HeartbeatInterval.Should().Be(heartbeatInterval);
-            subject.HeartbeatTimeout.Should().Be(__defaults.HeartbeatTimeout);
+            subject.HeartbeatTimeout.Should().Be(ServerSettings.DefaultHeartbeatTimeout);
         }
 
         [Fact]
@@ -66,7 +80,7 @@ public void constructor_with_heartbeatTimeout_should_initialize_instance()
 
             var subject = new ServerSettings(heartbeatTimeout: heartbeatTimeout);
 
-            subject.HeartbeatInterval.Should().Be(subject.HeartbeatInterval);
+            subject.HeartbeatInterval.Should().Be(ServerSettings.DefaultHeartbeatInterval);
             subject.HeartbeatTimeout.Should().Be(heartbeatTimeout);
         }
 

tests/MongoDB.Driver.Tests/MongoUrlBuilderTests.cs

@@ -457,7 +457,7 @@ public void TestHeartbeatInterval(int? ms, string formatString, string[] values)
             var built = new MongoUrlBuilder { Server = _localhost };
             if (heartbeatInterval != null) { built.HeartbeatInterval = heartbeatInterval.Value; }
 
-            var canonicalConnectionString = string.Format(formatString, values[0]).Replace("/?heartbeatFrequency=10s", "");
+            var canonicalConnectionString = string.Format(formatString, values[0]).Replace("/?heartbeatInterval=10s", "");
             foreach (var builder in EnumerateBuiltAndParsedBuilders(built, formatString, values))
             {
                 Assert.Equal(heartbeatInterval ?? ServerSettings.DefaultHeartbeatInterval, builder.HeartbeatInterval);