public function testDropUniqueConstraint()
 {
     $this->client->createUniqueConstraint('ToDrop', 'username');
     $this->assertArrayHasKey('ToDrop', $this->client->getUniqueConstraints()->getBody());
     $this->client->dropUniqueConstraint('ToDrop', 'username');
     $this->assertArrayNotHasKey('ToDrop', $this->client->getUniqueConstraints()->getBody());
 }