casper .start(casper.cli.get('baseUrl')+"?debug") .then(function () { this.wait(casper.cli.get('delay')); }) .then(function () { this.echo(casper.cli.get('baseUrl')+"?debug"); // If there was a JS error after the page load, casper won't perform asserts this.test.assertExists('html', 'Casper JS cannot assert DOM elements. A JS error has probably occured.'); this.test.assertExists('#drawing-canvas-container canvas', 'Check if drawing canvas element is created'); }) .run(function () { this.test.done(); });