Testing Laravel (5.1) console commands with phpunit

What is the best way to test Laravel console commands?

Here is an example of a command I'm running. It takes in a value in the constructor and in the handle method.

class DoSomething extends Command
{
    protected $signature = 'app:do-something';
    protected $description = 'Does something';

    public function __construct(A $a)
    {
        ...
    }

    public function handle(B $b)
    {
        ...    
    }
}

In my test class, I can mock both A and B, but I can't figure out how to pass $a in.

$this->artisan('app:do-something', [$b]);

Is it possible? Or am I going about this all wrong? Should I pass everything in thought the handle() method?

Thanks.

via Chebli Mohamed