less.js/test/browser/runner-main.js

describe("less.js", function() {

    var links = document.getElementsByTagName('link'),
        typePattern = /^text\/(x-)?less$/,
        testSheet = function(sheet) {
            it(sheet.id + " should match the expected output", function() {
                var lessOutputId =  sheet.id.replace("original-", ""),
                    expectedOutputId = "expected-" + lessOutputId,
                    lessOutput = document.getElementById(lessOutputId).innerText,
                    expectedOutputHref = document.getElementById(expectedOutputId).href,
                    expectedOutput = loadFile(expectedOutputHref);

                waitsFor(function() {
                    return expectedOutput.loaded;
                }, "failed to load expected outout", 10000);
                
                runs(function() {
                    // use sheet to do testing
                    expect(lessOutput).toEqual(expectedOutput.text);
                });
            });
        };

    for (var i = 0; i < links.length; i++) {
        if (links[i].rel === 'stylesheet/less' || (links[i].rel.match(/stylesheet/) &&
           (links[i].type.match(typePattern)))) {
            testSheet(links[i]);
        }
    }
});

var loadFile = function(href) {
    var request = new XMLHttpRequest(),
        response = { loaded: false, text: ""};
    request.open('GET', href, true);
    request.onload = function(e) {
        response.text = request.response;
        response.loaded = true;
    }
    request.send();
    return response;
};