Add assertions to ScriptFieldsUsageTests (#5219)

Author: russcam

tests/Tests/Search/Request/ScriptFieldsUsageTests.cs

@@ -3,6 +3,7 @@
 // See the LICENSE file in the project root for more information
 
 using System;
+using FluentAssertions;
 using Nest;
 using Tests.Core.ManagedElasticsearch.Clusters;
 using Tests.Domain;
@@ -85,5 +86,15 @@ public ScriptFieldsUsageTests(ReadOnlyCluster cluster, EndpointUsage usage) : ba
 					}
 				}
 			};
+
+
+		protected override void ExpectResponse(ISearchResponse<Project> response)
+		{
+			foreach (var fields in response.Fields)
+			{
+				fields.Value<int>("test1").Should().BeGreaterOrEqualTo(0);
+				fields.Value<double>("test2").Should().BeGreaterOrEqualTo(0);
+			}
+		}
 	}
 }