This code has been tested to work with casperjs 1.0.2 and phantomjs 1.9.1. After writing this, then I managed to get mocha-phantomjs (https://github.com/metaskills/mocha-phantomjs) to work and I switch to that. Primarily because mocha-phantomjs allows the usage of mocha's reporter straight without further customization. Additional things feature…

unit.js

// Check for phantom
if ( !phantom.casperLoaded ) {
    console.log( 'This script must be invoked using the casperjs executable' );
    phantom.exit( 1 );
}

// get a Casper object.
// See http://casperjs.org/
// Instantiate casper 
var casper = require('casper').create({
    exitOnError: false,
    pageSettings: {
        loadImages: false,
        loadPlugins: false
    },
    onLoadError: function (_casper, url) {
      console.log("[onLoadError]: ", url );
    },
    onTimeout: function (err) {
      console.log( "[Timeout]: ", err );
    },
    logLevel: 'debug',
    verbose: true
});

// Intercept events for 404 and other HTTP errors
casper.on('http.status.200', function(resource) {
    console.log("[HTTP 200]", " <", resource.url, ">" );
});

casper.on('http.status.404', function(resource) {
    console.log("[HTTP 404]", " <", resource.url, ">" );
});

casper.on('http.status.500', function(resource) {
    console.log("[HTTP 500]", " <", resource.url, ">" );
});

//
// Capture remote log messages
//
casper.on('remote.message', function(msg) {
  console.log(">>> ", msg);
});

casper.on('page.error', function(msg, trace) {
  console.log(">>> Remote error: ", msg, trace );
});


// this will be evaluated inside the context of the window.
// See http://casperjs.org/api.html#casper.evaluate for notes on
// the difference between casper's running environment and the 
// DOM environment of the loaded page.
function testReporter(){
  // casper is webkit, so we have good DOM methods. You're
  // probably unfamiliar with them because of shitty DOMs
  // in shitty browsers.  `test` is the class applied 
  // to passing tests in mocha. If you're using a different
  // runner, you'll need to figure out how to extract this
  // this kind of data from the report.
  var testNodes = document.querySelectorAll('.test');
  
  // testNodes is a NodeList so has no useful array methods,
  // but we can apply them, I'm returning an object that will
  // be used later:
  // {
  //    didPass: true
  //    text: 'The assertion of this test'
  // }
  return Array.prototype.map.call(testNodes, function(aTest){
    // in mocha, a passed test has a class `pass`. Normally a 
    // match will return an array of matches, which is `!!`ed
    // into an appropriate boolean.
    // the assertion of the test is stored in an `h2`
    return {
      didPass: !!aTest.getAttribute('class').match(/pass/),
      text: aTest.querySelector('h2').innerHTML
    }
  })
};

// open the casper's browser and load a url. This url should be
// where ever your unit tests are being displayed.
casper.start('http://localhost:9292/unit.html');

// Might need this code to wait for something to happen
// casper.waitForText("passes", function log(){
//    console.log( "Yap, got the passes text showing up, continue..." );
// });

// casper.then is a promise. It ensures specific execution order.
// give 'javascript promise' a google for some reading.
casper.then(function(){
  
  // this.evaluate runs the specified function inside the context
  // of the page that casper is accessing. Think of it like popping
  // open the console in Firebug or Webkit Inspector.
  // the return value of `evaluate` here is array of tests.
  this.evaluate(testReporter).forEach(function(assertion){
    // loop through the test, calling casper's `assert` method
    // which will print to the console.
    this.test.assert(assertion.didPass, assertion.text);
  },this);
});

// run all the `then`s and call `test.renderResults` when they're done.
casper.run(function(){
    if( this.cli.has( "xunit") )
    { 
        // This can help you to render to a file
        this.test.renderResults( true, 0, this.cli.get('xunit') );
    }
    else
    {
        this.test.renderResults( true );
    }
})