soContactSelectChange.js

var casper = require('casper').create();

casper.selectOptionByText = function(selector, textToMatch){
	this.evaluate(function(selector, textToMatch){
		var select = document.querySelector(selector),
			found = false;
		Array.prototype.forEach.call(select.children, function(opt, i){
			if (!found && opt.innerHTML.indexOf(textToMatch) !== -1) {
				select.selectedIndex = i;
			}
		});
	}, selector, textToMatch);
};

casper.start('http://stackoverflow.com/contact', function() {
    this.selectOptionByText("#topic", "quality");
});

casper.run(function(){
	this.capture("contact.png");
	this.echo("DONE");
	this.exit();
});