zombie.js(1) -- Insanely fast, headless full-stack testing using Node.js

The Bite

If you're going to write an insanely fast, headless browser, how can you not call it Zombie? Zombie it is.

Zombie.js is a lightweight framework for testing client-side JavaScript code in a simulated environment. No browser required.

Let's try to sign up to a page and see what happens:

var zombie = require("zombie");
var assert = require("assert");

// Load the page from localhost
zombie.visit("http://localhost:3000/", function (err, browser) {

  // Fill email, password and submit form
  browser.
    fill("email", "[email protected]").
    fill("password", "eat-the-living").
    pressButton("Sign Me Up!", function(err, browser) {

      // Form submitted, new page loaded.
      assert.equal(browser.text("title"), "Welcome To Brains Depot");

    })

});

Well, that was easy.

Walking

To start off we're going to need a browser. A browser maintains state across requests: history, cookies, HTML 5 local and session stroage. A browser has a main window, and typically a document loaded into that window.

You can create a new zombie.Browser and point it at a document, either by setting the location property or calling its visit function. As a shortcut, you can just call the zombie.visit function with a URL and callback.

The browser will load the document and if the document includes any scripts, also load and execute these scripts. It will then process some events, for example, anything your scripts do on page load. All of that, just like a real browser, happens asynchronously.

To wait for the page to fully load and all events to fire, you pass visit a callback function. This function takes two arguments. If everything is successful (page loaded, events run), the callback is called with null and a reference to the browser. If anything went wrong (page not loaded, event errors), the callback is called with an error.

If you worked with Node.js before you're familiar with this callback pattern. Every time you see a callback in the Zombie.js API, it works that way: the first argument is an error, or null if there is no error, with interesting value in the second argument.

Typically the second argument would be a reference to the browser or window object you called. This may seem redudant, but works suprisingly well when composing with other asynchronous APIs, for example, when using Zombie.js with Vows.

Whenever you want to wait for all events to be processed, just call browser.wait with a callback.

Read more on the Browser API

Hunting

There are several ways you can inspect the contents of a document. For starters, there's the DOM API, which you can use to find elements and traverse the document tree.

You can also use CSS selectors to pick a specific element or node list. Zombie.js implements the DOM Selector API. These functions are available from every element, the document, and the Browser object itself.

To get the HTML contents of an element, read its innerHTML property. If you want to include the element itself with its attributes, read the element's outerHTML property instead. Alternatively, you can call the browser.html function with a CSS selector and optional context element. If the function selects multiple elements, it will return the combined HTML of them all.

To see the textual contents of an element, read its textContent property. Alternatively, you can call the browser.text function with a CSS selector and optional context element. If the function selects multiple elements, it will return the combined text contents of them all.

Here are a few examples for checking the contents of a document:

// Make sure we have an element with the ID brains.
assert.ok(browser.querySelector("#brains"));

// Make sure body has two elements with the class hand.
assert.equal(browser.body.querySelectorAll(".hand").length, 2);

// Check the document title.
assert.equal(browser.text("title"), "The Living Dead");

// Show me the document contents.
console.log(browser.html());

// Show me the contents of the parts table:
console.log(browser.html("table.parts"));

CSS selectors are implemented by Sizzle.js. In addition to CSS 3 selectors you get additional and quite useful extensions, such as :not(selector), [NAME!=VALUE], :contains(TEXT), :first/:last and so forth. Check out the Sizzle.js documentation for more details.

Read more on the Browser API and CSS selectors

Feeding

You're going to want to perform some actions, like clicking links, entering text, submitting forms. You can certainly do that using the DOM API, or several of the convenience functions we're going to cover next.

To click a link on the page, use clickLink with selector and callback. The first argument can be a CSS selector (see Hunting) or the text contents of the A element you want to click. The second argument is a callback, which is passed on to browser.wait (see Walking). In other words, it gets fired after all events are processed, with error and browser as arguments.

Let's see that in action:

// Now go to the shopping cart page and check that we have
// three bodies there.
browser.clickLink("View Cart", function(err, browser) {
  assert.equal(browser.querySelectorAll("#cart .body"), 3);
});

To submit a form, use pressButton. The first argument can be a CSS selector, the button name (the value of the name argument) or the text that shows on the button. You can press any BUTTON element or INPUT of type submit, reset or button. The second argument is a callback, just like clickLink.

Of course, before submitting a form, you'll need to fill it with values. For text fields, use the fill function, which takes two arguments: selector and the field value. This time the selector can be a CSS selector, the field name (its name attribute), or the text that shows on the label associated with that field.

Zombie.js supports text fields, password fields, text areas, and also the new HTML 5 fields types like email, search and url.

The fill function returns a reference to the browser, so you can chain several functions together. Its sibling functions check and uncheck (for check boxes), choose (for radio buttons) and select (for drop downs) work the same way.

Let's combine all of that into one example:

// Fill in the form and submit.
browser.
  fill("Your Name", "Arm Biter").
  fill("Profession", "Living dead").
  select("Born", "1968")
  uncheck("Send me the newsletter").
  pressButton("Sign me up", function(err, browser) {
    // Make sure we got redirected to thank you page.
    assert.equal(browser.location, "http://localhost:3003/thankyou");
  });

Read more on the Browser API

Readiness

Zombie.js supports the following:

• HTML5 parsing and dealing with tag soups
• DOM Level 3 implementation
• HTML5 form fields (search, url, etc)
• C33 Selectors with some extensions
• Cookies and Web Storage
• XMLHttpRequest in all its glory
• setTimeout/setInterval and messing with the system clock
• pushState, popstate and hashchange events
• Scripts that use document.write

Reporting Glitches

Step 1: Run Zombie with debugging turned on, the trace will help figure out what it's doing. For example:

var browser = new zombie.Browser({ debug: true });
browser.visit("http://thedead", function(err, browser) {
  if (err)
    throw(err.message);
  ... 
});

Step 2: Wait for it to finish processing, then dump the current browser state:

brower.dump();

Step 3: If publicly available, include the URL of the page you're trying to access. Even better, provide a test script I can run from the Node.js console (similar to step 1 above).

Read more about troubleshooting

Giving Back

• Find assaf/zombie on Github
• Fork the project
• Add tests
• Make your changes
• Send a pull request

Read more about the guts of Zombie.js and check out the outstanding to-dos.

Brains

Zombie.js is copyright of Assaf Arkin, released under the MIT License

Zombie.js is written in CoffeeScript for Node.js

DOM emulation by Elijah Insua's JSDOM

HTML5 parsing by Aria Stewart's HTML5

CSS selectors by John Resig's Sizzle.js

XPath support using Google's AJAXSLT

Magical Zombie Girl by Toho Scope

See Also

zombie-api(7), zombie-troubleshoot(7), zombie-selectors(7), zombie-changelog(7), zombie-todo(7)