Fast-failing zombie test

When I outside-in tdd my last web feature, I find the following useful to have zombie failing with a helpful error message when unable to find an element in a page.

Here is an example of this in the prime-factors kata. The tip is in the fail().

Browser = require("zombie");

describe("decomposition", function() {

var home = "http://localhost:5000/index.html";
var browser = new Browser();

it("displays the decomposition of the input number", function(done) {
 browser.visit(home).
 then(function () {
 browser.fill("#number", "42")
 .clickLink("#decompose");
 }).
 then(function() {
 expect(browser.text("#decomposition")).toEqual("42 = 2 x 3 x 7");
 done();
 }).
 fail(function(error) {
 expect(error.toString()).toBeNull();
 done();
 });
}); 
});