This is an adaptation for Lumen of the Laravel Behat Extension package (https://github.com/laracasts/Behat-Laravel-Extension).

It's a custom Behat / Mink driver which extends the BrowserKit driver.

This will allow you to write functional tests using Behat (boot the Lumen application in a custom environment, mock components from the FeatureContext, requests are done directly on the application - no external requests).

To get started, you only need to follow a few steps:

As always, we need to pull in some dependencies through Composer.

composer require behat/behat behat/mink behat/mink-extension arisro/behat-lumen-extension --dev

This will give us access to Behat, Mink, and, of course, the Lumen extension.

If you want to use a custom .env file for the Behat tests you will need to modify bootstrap/app.php like this:

try {
    (new Dotenv\Dotenv(__DIR__.'/../', isset($dotEnvFile) ?: '.env'))->load();
} catch (Dotenv\Exception\InvalidPathException $e) {
    //
}

Next, within your project root, create a behat.yml file, and add:

default:
  autoload: [ %paths.base%/tests/functional/contexts ]
  extensions:
    Arisro\Behat\ServiceContainer\LumenExtension:
      # env_file: .env.behat
    Behat\MinkExtension:
      default_session: lumen
      lumen: ~
  suites:
    default:
      paths: [ %paths.base%/tests/functional/features ]
      filters:
      contexts:
        - FeatureContext

Optinally, you can specify a different .env file for your functional tests (with a test DB for example).

You have a very small example here https://github.com/arisro/behat-lumen-example.

Note: if you want to leverage some of the Mink helpers in your FeatureContext file, then be sure to extend Behat\MinkExtension\Context\MinkContext.