Cake\Database\Schema\SqliteSchema::constraintSql PHP Method

    public function constraintSql(Table $table, $name)
    {
        $data = $table->constraint($name);
        if ($data['type'] === Table::CONSTRAINT_PRIMARY && count($data['columns']) === 1 && $table->column($data['columns'][0])['type'] === 'integer') {
            return '';
        }
        $clause = '';
        if ($data['type'] === Table::CONSTRAINT_PRIMARY) {
            $type = 'PRIMARY KEY';
        }
        if ($data['type'] === Table::CONSTRAINT_UNIQUE) {
            $type = 'UNIQUE';
        }
        if ($data['type'] === Table::CONSTRAINT_FOREIGN) {
            $type = 'FOREIGN KEY';
            $clause = sprintf(' REFERENCES %s (%s) ON UPDATE %s ON DELETE %s', $this->_driver->quoteIdentifier($data['references'][0]), $this->_convertConstraintColumns($data['references'][1]), $this->_foreignOnClause($data['update']), $this->_foreignOnClause($data['delete']));
        }
        $columns = array_map([$this->_driver, 'quoteIdentifier'], $data['columns']);
        return sprintf('CONSTRAINT %s %s (%s)%s', $this->_driver->quoteIdentifier($name), $type, implode(', ', $columns), $clause);
    }

 /**
  * Test the constraintSql method.
  *
  * @dataProvider constraintSqlProvider
  */
 public function testConstraintSql($name, $data, $expected)
 {
     $driver = $this->_getMockedDriver();
     $schema = new SqliteSchema($driver);
     $table = (new Table('articles'))->addColumn('title', ['type' => 'string', 'length' => 255])->addColumn('author_id', ['type' => 'integer'])->addConstraint($name, $data);
     $this->assertEquals($expected, $schema->constraintSql($table, $name));
 }