public function testPushAndPop()
 {
     $a = new VersionTransducer(new TestVersionProvider());
     $observer = $this->getMockBuilder('TestMigration1')->setConstructorArgs(array('2016-01-01-230556'))->setMethods(array('migrate'))->getMock();
     $observer->expects($this->never())->method('migrate');
     $a->addMigration($observer);
     $a->addMigration($this->createMigration('2016-01-01-230557'));
     $a->addMigration($this->createMigration('2016-01-01-230558'));
     $a->addMigration($this->createMigration('2016-01-01-230559'));
     $a->migrateUp();
 }
 protected function execute(InputInterface $input, OutputInterface $output)
 {
     $output->writeln(VersionTransducer::createVersionName());
 }