Introduction

BDD, Behat, Mink and other Wonderful Things Tutorial

Add to Shopping Cart
 

Introduction

Hey! Welcome to the tutorial that we’re calling “All about the World of Behat”. Our goal is simple: to understand the Behavior-Driven Development philosophy and master two tools - Behat & Mink - that will make you a functional-testing legend.

Tip

Behat and Mink have been developed by the open source community and are led by our friend and yours: Konstantin Kudryashov - aka @everzet: http://twitter.com/everzet. He was a huge help in the creation of this course!

Why test your application? Well imagine you are running Jurassic Park, you need to know that adding the new Pterodactyl exhibit won’t turn off the electric fence around the velociraptor pen. Don’t have any tests? Good luck - they know how to open doors.

Getting good at practicing behavior-driven development - or BDD - means more than learning a new tool, it will change your entire development process for the better. Imagine a world where communication on your team is perfect, you always deliver exactly what your client wanted, electricity on the velociraptor fence never goes down and chocolate ice cream is free. Ok, we can’t promise all of that, but we’ll see how BDD makes developing fun all over again.

In this first part, I’m going to show you how to install everything you need and write your first feature and scenarios. After that, we’ll back up to learn more about each important part: scenarios & features, step definitions, advanced Mink, and other really important topics.

Installation

Before we begin, let’s install a few libraries. Start by creating a new directory and adding a composer.json file.

Note

If you’re testing an existing application, do all of this inside your project directory.

Composer is a tool that helps download external libraries into your project. If you’re not familiar with it, it’s totally ok! We have a free course that explains it.

Note

Watch “The Wonderful World of Composer Tutorial” at http://bit.ly/KnpU-Composer

We’ll be downloading Behat, Mink, and a few other related libraries into our project. To make this easy, we’ve prepared a gist with exactly what you need to add to your composer.json.

{
    "require": {
        "behat/mink": "1.4@stable",
        "behat/mink-goutte-driver": "*",
        "behat/mink-selenium2-driver": "*",
        "behat/behat": "2.4@stable",
        "behat/mink-extension": "*"
    },
    "minimum-stability": "dev",
    "config": {
        "bin-dir": "bin/"
    }
}

Tip

If you’re using Behat in a Symfony2 project, you’ll also want to include the Symfony2 Extension.

Next, download Composer by going to GetComposer.org and clicking download. Copy one of the two code blocks, depending if you have curl installed, and paste into the terminal. This downloads a standalone composer.phar executable.

Tip

Remember, we talk a lot more about composer in “The Wonderful World of Composer Tutorial” at http://bit.ly/KnpU-Composer

Next, tell Composer to download the libraries we need by running php composer.phar install

$ php composer.phar install --prefer-dist

We’ll fast-forward through this thrilling process as it downloads each library and places it into a new vendor/ directory. When it’s finished, you’ll also notice a new bin/ directory with a behat file in it. This is the Behat executable, and you’ll use it to run your tests and get debug information.

Next, create a behat.yml file at the root of the project. When Behat runs, it looks for a behat.yml file, which it uses for its configuration.

Tip

For more information about the behat.yml configuration file, see Configuration - behat.yml.

We’ll use it to activate MinkExtension, which is like a plugin for Behat. Also, we’re going to test Wikipedia, so use it as the base_url. If you’re testing your application, use its local base URL instead. Hopefully you’ll join us for the rest of this course, where we’ll go into greater detail.

default:
  extensions:
    Behat\MinkExtension\Extension:
      goutte:    ~
      selenium2: ~
      base_url: http://en.wikipedia.org/

Note

If you’re using Behat with Symfony2, you should also activate the Symfony2 Extension that you added to composer.json:

default:
  extensions:
    # ... the MinkExtension code
    Behat\Symfony2Extension\Extension: ~

To get the project ready to use Behat, run php bin/behat --init. This creates a features/ directory and a bootstrap/FeatureContext.php file inside of it.

Note

If you’re using Behat in Symfony2, run the command for a specific bundle. A Features directory will be created in that bundle, with a similar structure. If the directory is created at the root of your project, delete it and double-check that you’ve activated the Symfony2Extension in the behat.yml file:

$ php bin/behat @EventBundle --init

Open this file and make it extend MinkContext instead of BehatContext:

// ...
use Behat\MinkExtension\Context\MinkContext;

class FeatureContext extends MinkContext
{
    .. ///
}

Later on, we’ll learn more about Behat and Mink individually, and the importance of the MinkContext class will make more sense.

Woo! With all that installing and configuring behind us, let’s get to locking down the raptor cage!

Writing Features and running tests

The Behat and Mink libraries are most commonly used to test web applications. You describe a feature in a human-readable syntax called Gherkin, then execute these as tests. The best way to see this in action is to take your DeLorean back to the past a few years and imagine that Jimmy Wales has asked you to build Wikipedia.org. Yes, we know this site actually exists, but we’re going to describe its behavior and run some functional tests against it.

First, forget about tests. Our goal is to describe the feature. We’re going to describe the Wikipedia search, so create a search.feature file in the features directory. The language in this file is called Gherkin and you start by describing the feature using a specific, four-line syntax. This defines the business value of the feature, who will benefit from it, and a short description. So, when John Hammond comes to you with a big idea, your first goal should be to try to describe it using these four lines. Writing good feature descriptions is really important, and we’ll spend more time on this later.

Feature: Search
  In order to find a word definition
  As a website user
  I need to be able to search for a word

Each feature has many scenarios, which describe the specific behavior of the feature. Each scenario has 3 sections. Given which details the starting state of the system, When which includes the action the user takes, and Then which describes what the user sees after taking action. In this scenario, we’re searching for an exact article that matches.

Feature:
  # ...

  Scenario: Search for a word that exists
    Given I am on "/wiki/Main_Page"
    When I fill in "search" with "Velociraptor"
    And I press "searchButton"
    Then I should see "an enlarged sickle-shaped claw"

Great! In a normal application, we’d now start developing the feature until it it fits our description of its behavior. But since Wikipedia exists already, we can see the behavior in action!

Writing Features and Scenarios is great, because it helps clarify how something should work in human-readable language. But the real magic is that we can run the scenario as a functional test!

To do this, run php bin/behat. Behind the scenes, this reads the scenario and actually uses a real browser to go to Wikipedia, fill in the field, and click the button!

To see how this is possible, execute Behat, but pass a -dl option:

$ php bin/behat -dl

Behat’s job is to read each line in the scenario and execute some function inside our FeatureContext class. Because we’re using Mink, we inherit a lot of common sentences. You can use these to write tests without writing any PHP code. You can also invent your own sentence and then create a new method in the FeatureContext class. We’ll talk a lot more about this later.

Executing Tests that use JavaScript

Our first scenario ran in the background using a headless browser called Goutte. Goutte runs very fast, you know like a velociraptor, but it doesn’t support Javascript. This was ok because our Scenario doesn’t rely on any JavaScript functionality. But what if it did? Can we test things that use JavaScript?

Of course! And with Behat & Mink, it’s incredibly easy. First, download Selenium Server, which is just a jar file that can live anywhere on your computer. Start Selenium at the command line by running java -jar followed by the filename.

$ java -jar selenium-server-standalone-2.28.0.jar

Now for the magic. To make this one scenario execute using Selenium instead of Goutte, add an @javascript tag above the scenario. Now just re-run your Behat tests using the same command as before:

$ php bin/behat

Magically, a browser opens up, surfs to Wikipedia, fills in the field and presses the button. This is the most powerful feature of Mink: you can run some tests using Goutte and other tests - that require JavaScript - in Selenium simply by adding the @javascript tag.

Digging into Gherkin, Behat and Mink

We now have a project using Behat & Mink, and our first feature file and scenario. Using a bunch of built-in english sentences, we’re able to write tests without any work at all.

But to really get good, we need to dive deeper to find out how to write really solid Feature files, how to create your own custom sentences, how to master Mink to do really complex Browser tasks, and much more. So, keep going!

Leave a comment!

Back to the screencasts list