fix on mock in a test

frontend-js/src/test/js/helper.js

@@ -2,6 +2,8 @@
 
 require("./mocha-config");
 
+var logger = require('./logger');
+
 var Alias = require("../../main/js/map/data/Alias");
 var AbstractCustomMap = require("../../main/js/map/AbstractCustomMap");
 var ChemicalDbOverlay = require("../../main/js/map/overlay/ChemicalDbOverlay");
@@ -181,6 +183,9 @@ Helper.prototype.createDbOverlay = function(map) {
     map : map,
     name : "search",
   });
+  result.clear = function(){
+    logger.debug("Clear mock");
+  };
   map.registerSource(result);
   return result;
 };