finding is point laying on line or not in esri map using arcgis API

I am trying to find whether the point lies on the line or not as below

 function identifyFeatures(evt){
     var extentGeom = pointToExtent(map,evt.mapPoint,10);
     var filteredGraphics = dojo.filter(testLayer.graphics, function(gg) {
         if(extentGeom.contains(gg.geometry.getExtent())){
             return extentGeom.contains(gg.geometry.getExtent());
         } else {
             return gg.geometry.getExtent().contains(extentGeom);
         } 
      });
      var content = "";
      content = "<i>Total Features: " + filteredGraphics.length + "</i>";
      map.infoWindow.setContent(content);
      map.infoWindow.setTitle("Identify Results");
      var anchor = map.getInfoWindowAnchor(evt.screenPoint);
      map.infoWindow.show(evt.screenPoint,anchor);
 };

I am using contains method of extent and trying to check whether clicked point extent is falling on line extent or line extent is falling on clicked point extent.But if I click on the center of the line then only I am getting features. You can see the code fiddle

can any one suggest me is there any other way to check whether point lies on line or not?

You should just filter graphics if the extent of the point (padded with your extentToPoint() function) intersects() with the geometry of the line.

  function identifyFeatures(evt){
      var extentGeom = pointToExtent(map,evt.mapPoint,10);
      var filteredGraphics = dojo.filter(testLayer.graphics, function(gg) {
        return extentGeom.intersects(gg.geometry);
      });
      var content = "<i>Total Features: " + filteredGraphics.length + "</i>";
      map.infoWindow.setContent(content);
      map.infoWindow.setTitle("Identify Results");
      map.infoWindow.show(evt.screenPoint,map.getInfoWindowAnchor(evt.screenPoint));
  };

see a working demo: https://jsfiddle.net/q68rzde2/1/