public function testAddingTimeStamps()
 {
     $blueprint = new Blueprint('users');
     $blueprint->timestamps();
     $statements = $blueprint->toSql($this->getConnection(), $this->getGrammar());
     $this->assertEquals(1, count($statements));
     $this->assertEquals('alter table users add ( created_at timestamp not null, updated_at timestamp not null )', $statements[0]);
 }