[OpenLayers-Dev] Constructor trouble when testing new control

[Ian Mayo]

I'm afraid I can't get my head around an error that's being thrown by
my test at:
http://trac.openlayers.org/browser/sandbox/ianmayo/openlayers/tests/Control/test_ScaleLine.html

when I execute the following line in test_01_Control_ScaleLine_constructor:
control = new OpenLayers.Control.ScaleLine();

I get this error reported:
test_01_Control_ScaleLine_constructor planned 2 assertions but got 0;
fail 0 ok 0
exception: : object: [Exception... "Illegal operation on WrappedNative
prototype object" nsresult: "0x8057000c
(NS_ERROR_XPC_BAD_OP_ON_WN_PROTO)" location: "JS frame ::
file:///home/ian/dev/openlayers/openlayers/lib/OpenLayers/Util.js ::
anonymous :: line 60" data: no]

The guilty line is calling my constructor in
http://trac.openlayers.org/browser/sandbox/ianmayo/openlayers/lib/OpenLayers/Control/ScaleLine.js:
initialize: function(element, options) {
   OpenLayers.Control.prototype.initialize.apply(this, arguments);
   this.element = OpenLayers.Util.getElement(element);
},

I have to admit, I don't fully understand how the
constructor/initialiser model is working.

The other tests in the module all work - and demonstrate parameters
being used in the constructor.

I'd really appreciate a pointer in either the correct way to handle
parameters in the constructor, or the correct way to use the
parameters in the constructor.

cheers,
Ian.