public function primary()
    {
        $key = $this->tableHasPrimary()->getPrimaryKey();
        $message = "The column {$this->name} is not a primary key.";

        return $this->assertTrue(in_array($this->name, $key->getColumns()), $message)
                    ->assertTrue($key->isPrimary())
                    ->assertTrue($key->isUnique());
    }