add tests trying to replicate #2136 to no avail, found a nasty bug where number_of_replicas can get overriden to null when calling update index settings

Conflicts:
	src/Nest/IndexModules/IndexSettings/Settings/IndexSettingsConverter.cs

Author: Mpdreamz

src/Nest/IndexModules/IndexSettings/Settings/IndexSettingsConverter.cs

@@ -75,9 +75,11 @@ public override void WriteJson(JsonWriter writer, object value, JsonSerializer s
 			d[UpdatableIndexSettings.SlowlogIndexingSource] = indexing?.Source;
 
 			var indexSettings = value as IIndexSettings;
-			d["index.number_of_shards"] = indexSettings?.NumberOfShards;
-			d[UpdatableIndexSettings.NumberOfReplicas] = indexSettings?.NumberOfReplicas;
-			d[UpdatableIndexSettings.StoreType] = indexSettings?.FileSystemStorageImplementation;
+			if (indexSettings != null)
+			{
+				d["index.number_of_shards"] = indexSettings?.NumberOfShards;
+				d[UpdatableIndexSettings.StoreType] = indexSettings?.FileSystemStorageImplementation;
+			}
 			d["index.queries.cache.enabled"] = indexSettings?.Queries?.Cache?.Enabled;
 
 			d[UpdatableIndexSettings.Analysis] = ds.Analysis;

src/Tests/Indices/IndexSettings/GetIndexSettings/GetIndexSettingsApiTests.cs

@@ -1,5 +1,8 @@
 using System;
+using System.Linq;
+using System.Threading.Tasks;
 using Elasticsearch.Net;
+using FluentAssertions;
 using Nest;
 using Tests.Framework;
 using Tests.Framework.Integration;
@@ -33,5 +36,15 @@ protected override LazyResponses ClientUsage() => Calls(
 		{
 			Local = true
 		};
+
+		protected override void ExpectResponse(IGetIndexSettingsResponse response)
+		{
+			response.Indices.Should().NotBeEmpty();
+			var index = response.Indices.First().Value;
+			index.Should().NotBeNull();
+			index.Settings.NumberOfShards.Should().HaveValue().And.BeGreaterThan(0);
+			index.Settings.NumberOfReplicas.Should().HaveValue();
+		}
+
 	}
-}
+}

src/Tests/Indices/IndexSettings/UpdateIndicesSettings/UpdateIndexSettingsApiTests.cs

@@ -27,20 +27,23 @@ protected override LazyResponses ClientUsage() => Calls(
 
 		protected override object ExpectJson { get; } = new Dictionary<string, object>
 		{
-			{ "index.blocks.write", false }
+			{ "index.blocks.write", false },
+			{ "index.number_of_replicas", 2 }
 		};
 
 		protected override Func<UpdateIndexSettingsDescriptor, IUpdateIndexSettingsRequest> Fluent => d => d
 			.IndexSettings(i => i
 				.BlocksWrite(false)
+				.NumberOfReplicas(2)
 			);
 
 		protected override UpdateIndexSettingsRequest Initializer => new UpdateIndexSettingsRequest
 		{
 			IndexSettings = new Nest.IndexSettings
 			{
-				BlocksWrite = false
+				BlocksWrite = false,
+				NumberOfReplicas = 2
 			}
 		};
 	}
-}
+}