Now that we've seen what we can theoretically do with Codeception, let's move on and install it.

Yii comes with its own Codeception extension that provides a base class for unit tests (yii\codeception\TestCase), a class for tests that require database interaction (yii\codeception\DbTestCase), and a base class for Codeception page objects (yii\codeception\BasePage).

As usual, our preferred method is using Composer:

$ composer require "codeception/codeception: 2.0.*" --prefer-dist --dev

There's a specific reason to use –prefer-dist; if you're using Git, you can get into a hairy situation with Git submodules (but again excluding the /vendor folder should solve most of these problems). To avoid repeating it every time we use Composer, just add the following to your composer.json file:

// composer.json

{
    "config": {
        "preferred-install": "dist"
    }
}

Also, remember that using composer install will not work if you've added the component manually to your...