Joy of Think

var tag;
var func = function(){
return afunc( tag );
}

is not a correct usage.

The correct one is:

var genFunc = function( ptag ){
var ltag = ptag;
return function(){afunc( ltag )};
};

genFunc( tag );

1, Add message to Assert statement to make code easy.
2, Use subscribe() listen custom event of TestRunner.
3, Use YAHOO.log() to output log.
4, var Assert = YAHOO.util.Assert to use YAHOO's assert.

Link: http://eriwen.com/javascript/js-stack-trace/

Nice article.