AdamWathan\Form\Elements\Select::multiple PHP Method

    public function multiple()
    {
        $name = $this->attributes['name'];
        if (substr($name, -2) != '[]') {
            $name .= '[]';
        }
        $this->setName($name);
        $this->setAttribute('multiple', 'multiple');
        return $this;
    }

 public function testCanSelectMultipleElementsInMultiselects()
 {
     $select = new Select('color', array('red' => 'Red', 'blue' => 'Blue'));
     $expected = '<select name="color[]" multiple="multiple"><option value="red" selected>Red</option><option value="blue" selected>Blue</option></select>';
     $result = $select->multiple()->select(array('red', 'blue'))->render();
     $this->assertEquals($expected, $result);
 }