I did it with no problems. For example, I have a command that is run periodically via a CRON job and sends an email report

class SendEmailCommandTest extends TestCase {

    public function tearDown()
    {
        Mockery::close();
    }

    public function test_fire()
    {
        // given
        //
        $cmd = Mockery::mock("\MyApp\Commands\SendEmailCommand[argument, send]");

        $cmd->shouldReceive("argument")
            ->with("name")
            ->once()
            ->andReturn("my-email-name");

        $cmd->shouldReceive("send")
            ->with("my-email-name")
            ->once();

        // when
        //
        $cmd->fire();

        // then
        //
        $this->assertTrue(true);
    }

}

The test works by creating a partial mock of the command class, mocking the argument and send methods. The argument method is the Laravel method that returns a command line argument - here the mock just returns a value. The send method is a method I wrote to do the work (basically it just calls the send method on a library class that's tested elsewhere). The fire method doesn't return any values, so I included a "dummy" test at the end - the real test ensures that the appropriate methods are called with the right arguments.