Using phpspec for testing Symfony2 Commands
You can use PhpSpec to test Command in a unit testable way - it's not too bad but you end up with a lot of mocking of input/output.
It's better to keep your Commands nice and small, with them delegating to other services that are unit tested - then you can cover with Behat and get your confidence that they're working.
It's a very similar problem to testing Controllers, just that Commands have more dependencies to mock if you try the unit testing approach.