Added unit test

Author: rjperes

src/NHibernate.Test/MappingByCode/ExplicitMappingTests/BasicMappingOfSimpleClass.cs

@@ -1,4 +1,6 @@
 using System;
+using System.Collections;
+using System.Collections.Generic;
 using System.Linq;
 using NHibernate.Cfg.MappingSchema;
 using NHibernate.Mapping.ByCode;
@@ -32,6 +34,24 @@ public void MapClassWithIdAndProperty()
 			ModelIsWellFormed(hbmMapping);
 		}
 
+		[Test]
+		public void MapClassWithIdAndPropertyWithParamsDictionary()
+		{
+			var mapper = new ModelMapper();
+			mapper.Class<MyClass>(ca =>
+			{
+				ca.Id(x => x.Id, map =>
+				{
+					map.Column("MyClassId");
+					//NH-3415
+					map.Generator(Generators.HighLow, gmap => gmap.Params(new Dictionary<string, object> { { "max_low", 100 } }));
+				});
+				ca.Property(x => x.Something, map => map.Length(150));
+			});
+			var hbmMapping = mapper.CompileMappingFor(new[] { typeof(MyClass) });
+			ModelIsWellFormed(hbmMapping);
+		}
+
 		[Test]
 		public void WhenMapClassWithoutIdThenApplyTypeOfGeneratorDef()
 		{