added unit tests for the various terms aggregation options

Author: Mpdreamz

src/Tests/Nest.Tests.Unit/Search/Aggregations/Terms/TermAggregationSerializes.json

@@ -0,0 +1,9 @@
+{
+  "field": "country",
+  "min_doc_count": 1,
+  "execution_hint": "global_ordinals_low_cardinality",
+  "order": {
+    "_count": "asc"
+  },
+  "collect_mode": "breadth_first"
+}

src/Tests/Nest.Tests.Unit/Search/Aggregations/Terms/TermAggregationTests.cs

@@ -0,0 +1,23 @@
+using System.Reflection;
+using Nest.Tests.MockData.Domain;
+using NUnit.Framework;
+
+namespace Nest.Tests.Unit.Search.Aggregations.Terms
+{
+	[TestFixture]
+	public class TermAggregationTests : BaseJsonTests
+	{
+		[Test]
+		public void TermAggregationSerializes()
+		{
+			var s = new TermsAggregationDescriptor<ElasticsearchProject>()
+				.CollectMode(TermsAggregationCollectMode.BreadthFirst)
+				.ExecutionHint(TermsAggregationExecutionHint.GlobalOrdinalsLowCardinality)
+				.Field(p => p.Country)
+				.MinimumDocumentCount(1)
+				.OrderAscending("_count");
+
+			this.JsonEquals(s, MethodBase.GetCurrentMethod());
+		}
+	}
+}