Testing a Knp ConsoleServiceProvider Command

CommandTestCase.php

<?php

namespace MyApp\Test;

use Knp\Console\ConsoleEvent;
use Knp\Console\ConsoleEvents;
use Silex\Application;
use Knp\Console\Application as ConsoleApplication;
use Symfony\Component\Console\Input\StringInput;
use Symfony\Component\Console\Output\BufferedOutput;

/**
 * Command test base class
 *
 * Used for tests of Command classes
 */
abstract class CommandTestCase extends WebTestCase
{
    /**
     * Runs the specified console command and returns the output
     *
     * @param string $command Command and arguments specified as a single string
     * @return string The output of the command
     */
    protected function runCommand(string $command): string
    {
        $input = new StringInput($command);
        $output = new BufferedOutput();

        $application = $this->getConsoleApplication($this->createApplication());
        $application->run($input, $output);

        return $output->fetch();
    }

    /**
     * Creates a ConsoleApplication
     *
     * @param Application $app
     * @return ConsoleApplication
     */
    protected function getConsoleApplication(Application $app): ConsoleApplication
    {
        $application = new ConsoleApplication(
            $app,
            __DIR__ . '/../../..',
            'MyApp',
            '0.0.1'
        );

        $application->setAutoExit(false);

        $this->registerCommands($app, $application);

        return $application;
    }

    /**
     * Register commands on the console application
     *
     * Uses the typical INIT event to register commands the normal way. You could also override this method if you
     * want to test Commands in isolation (call $application->add() yourself)
     *
     * @param Application        $app
     * @param ConsoleApplication $application
     */
    protected function registerCommands(Application $app, ConsoleApplication $application)
    {
        $app['dispatcher']->dispatch(ConsoleEvents::INIT, new ConsoleEvent($application));
    }
}

SomethingTest.php

<?php

namespace MyApp\Something;

use MyApp\Test\CommandTestCase;

class SomethingTest extends CommandTestCase
{
    public function testWithSomeArguments()
    {
        $output = $this->runCommand('some:command --with-args');
        $this->assertStringStartsWith('Hello, world!', $output);
    }
}

The MyApp\Test\WebTestCase that is being extended by the CommandTestCase is just a simple implementation of Silex\WebTestCase (i.e. it defines createApplication(): Silex\Application)