Tests and fixes
diff --git a/src/ProtocolBuffers/GeneratedBuilder.cs b/src/ProtocolBuffers/GeneratedBuilder.cs
index 01d3d2d..2ec2762 100644
--- a/src/ProtocolBuffers/GeneratedBuilder.cs
+++ b/src/ProtocolBuffers/GeneratedBuilder.cs
@@ -158,6 +158,10 @@
           this[field] = entry.Value;
         }
       }
+
+      //Fix for unknown fields not merging, see java's AbstractMessage.Builder<T> line 236
+      MergeUnknownFields(other.UnknownFields);
+
       return ThisBuilder;
     }