Testing Symfony commands with Behat

The other day I was creating a Symfony command that will be periodically executed by a cronjob. I decided to write a Behat test for it, to see what a test like that would look like. Plus, just because it is executed by the system from a command line, doesn’t mean we can skimp on the business requirements.

We need Symfony, Behat, and Behat Symfony2 extension. In the behat.yml file we configure the Behat extension to boot up the Kernel for us and pass it in is a constructor argument to our Behat Context:

default:
    extensions:
        Behat\Symfony2Extension:
          kernel:
            bootstrap: features/bootstrap/bootstrap.php
            class: App\Kernel

    suites:
      system:
        paths:
          - '%paths.base%/features/system.feature'
        contexts:
          - SystemContext:
              kernel: '@kernel'

We enable and configure the Behat Symfony2 extension, and tell Behat that the system suite will use the system.feature feature file and the SystemContext context which takes one constructor argument, the kernel. I don’t like to put everything into the default FeatureContext for Behat, but rather split different contexts into, well, different contexts. That’s why I created the separate SystemContext.

The boostrap.php file is created when installing the extension (at least, it was created for me as I installed it using Symfony Flex):

<?php
putenv('APP_ENV='.$_SERVER['APP_ENV'] = $_ENV['APP_ENV'] = 'test');
require dirname(__DIR__, 2).'/config/bootstrap.php';

The system.feature file doesn’t have much, just an example scenario:

Feature: System executed commands

  Scenario: Behat testing a Symfony command
    Given I am the system
    When I greet the world
    Then I should say "Hello World"

The SystemContext

The SystemContext file is where it gets interesting:

<?php

use App\Kernel;
use Behat\Behat\Context\Context;
use Symfony\Bundle\FrameworkBundle\Console\Application;
use Symfony\Component\Console\Input\ArgvInput;
use Symfony\Component\Console\Output\BufferedOutput;
use Webmozart\Assert\Assert;

class SystemContext implements Context
{
    /**
     * @var Application
     */
    private $application;

    /**
     * @var BufferedOutput
     */
    private $output;

    public function __construct(Kernel $kernel)
    {
        $this->application = new Application($kernel);
        $this->output = new BufferedOutput();
    }

It implements the Behat Context interface so that Behat recognizes it as a context.

In the constructor we create a new console Application with the Kernel that the Behat Symfony2 extension created for us. We will use this application instance to run the command that we are testing. For all intents and purposes, this application instance acts the same as the application instance that gets created in the bin/console script that we usually use to run Symfony commands.

We also create a BufferedOutput in the constructor, that will hold the output that the command produces, which we can later on use to assert did the command produce the desired output.

Behat step definitions

The steps are defined like so (it’s in the same SystemContext.php file as the previous example):

<?php

class SystemContext implements Context
{
    /**
     * @Given I am the system
     */
    public function iAmTheSystem()
    {
        Assert::same('cli', php_sapi_name());
    }

    /**
     * @When I greet the world
     */
    public function iGreetTheWorld()
    {
        $command = 'app:hello-world';
        $input = new ArgvInput(['behat-test', $command, '--env=test']);
        $this->application->doRun($input, $this->output);
    }

    /**
     * @Then I should say :sentence
     */
    public function iShouldSay($sentence)
    {
        $output = $this->output->fetch();

        Assert::same($sentence, $output);
    }

I am the system

In the first Behat step we assert that the PHP interface is the cli. Not sure how it could be anything else in this case, but let’s have that in there.

I greet the world

The second Behat step is where the fun part happens, where we run the command. The ArgvInput takes an array of parameters from the CLI in the argv format. In the case of bin/console it ends up being populated from $_SERVER['argv']. In this case though, we need to populate it on our own.

The first argument is always the name that was used to run the script and it ends up being just a “placeholder”, hence the behat-test value. We can put in anything there, really.

The second parameter is the command that we want to run: app:hello-world. It is the same string we would use when executing that command through bin/console. Because we created an instance of the Application in the constructor, Symfony will know exactly what command that is.

The third parameter is an option to tell Symfony to run the command in the test environment.

Once we have the input ready, we tell the application to run using the doRun method, passing in the input and the output (which is a BufferedOutput).

I should say :sentence

In the third Behat step we fetch the output and assert that it is the same as the output we expected it to be.

Make it reusable

To make it a bit more reusable, the running of the command in the iGreetTheWorld step can be extracted to a private method so that it all reads a little bit nicer. The final result looks something like this:

<?php

use App\Kernel;
use Behat\Behat\Context\Context;
use Symfony\Bundle\FrameworkBundle\Console\Application;
use Symfony\Component\Console\Input\ArgvInput;
use Symfony\Component\Console\Output\BufferedOutput;
use Webmozart\Assert\Assert;

class SystemContext implements Context
{
    /**
     * @var Application
     */
    private $application;

    /**
     * @var BufferedOutput
     */
    private $output;

    public function __construct(Kernel $kernel)
    {
        $this->application = new Application($kernel);
        $this->output = new BufferedOutput();
    }

    /**
     * @Given I am the system
     */
    public function iAmTheSystem()
    {
        Assert::same('cli', php_sapi_name());
    }

    /**
     * @When I greet the world
     */
    public function iGreetTheWorld()
    {
        $this->runCommand('app:hello-world');
    }

    /**
     * @Then I should say :sentence
     */
    public function iShouldSay($sentence)
    {
        $output = $this->output->fetch();

        Assert::same($sentence, $output);
    }

    private function runCommand(string $command)
    {
        $input = new ArgvInput(['behat-test', $command, '--env=test']);
        $this->application->doRun($input, $this->output);
    }

Happy hackin’!