casperiteration.js

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

casper.userAgent('Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)'); 

var userNames = ['username1','username2','username3','username4'];
var passWords = ['password1','password2','password3','password4'];

var url = 'http://somesite.com';

function login(username, password) {
	casper.then(function () {
		this.sendKeys('#log', username);
		this.sendKeys('#pwd', password);
		
		this.click('#wpmem_login > form > fieldset > div.button_div > input.buttons');
		console.log("Log In button has been clicked!")
	});

    casper.wait(5000, function () {
        this.echo(this.getTitle());
        this.echo(this.fetchText('#wp-admin-bar-my-account > a'));
        casper.capture('pic_'+username+'.png');
    });
};

casper.start(); // empty page

casper.viewport(1024, 768);

userNames.forEach(function(username, index){
    casper.thenOpen(url); // open the start page
    login(username, passWords[index]); // schedule the steps
});

casper.run(); // begin the execution