PHP Class which fails unit testing

<?php
/**
 * Model for a Client
 *
 * This class holds generic information about a client of a project, providing
 * first steps for multi-client-support of the application.
 *
 * @author Manuel Stosic
 */
class Application_Model_Client
{
//region Properties

  /**
   * Filters
   *
   * All filters for this model data
   *
   * @var     array
   * @access  protected
   */
  protected $_filters;

  /**
   * Validators
   *
   * All validators for this model data
   *
   * @var     array
   * @access  protected
   */
  protected $_validators;

  /**
   * Client ID
   *
   * @var int
   * @access protected
   */
  protected $_id = 0;

  /**
   * Client Name
   *
   * @var string
   * @access protected
   */
  protected $_name;

  /**
   * Client Description
   *
   * @var string
   * @access protected
   */
  protected $_description;

  /**
   * Client Flag Active
   *
   * @var bool
   * @access protected
   */
  protected $_flag_active;

  /**
   * Client Flag Deleted
   *
   * @var bool
   * @access protected
   */
  protected $_flag_deleted;

//endregion

//region Magic functions

  /**
   * __construct()
   *
   * Constructor which sets the filters and validators
   *
   * @access public
   * @param   mixed[] $props Array || StdClass of Properties
   */
  public function __construct($props = null)
  {
    // Set Filters
    $this->_filters = array(
      'id'            => array(),
      'name'          => array('StringTrim', 'StripTags'),
      'description'   => array('StringTrim', 'StripTags'),
      'flag_active'   => array(),
      'flag_deleted'  => array()
    );

    // Set Validators
    $this->_validators = array(
      'id'            => array('Int'),
      'name'          => array(new Zend_Validate_StringLength(array('min'=>4, 'max'=>50)), new Zend_Validate_Alnum(true)),
      'description'   => array(new Zend_Validate_StringLength(array('max'=>5000))),
      'flag_active'   => array(),
      'flag_deleted'  => array()
    );

    // Set Properties
    if (!is_null($props)) {
      $this->populate($props);
    }
  }

//endregion

//region Setters and getters

  /**
   * setId()
   *
   * Sets the ID of the Client Model
   *
   * @param int $id ID of the Client
   * @access public
   * @return Application_Model_Client
   */
  public function setId($arg)
  {
    $input = new Zend_Filter_Input($this->_filters, $this->_validators);
    $input->setData(array('id'=>$arg));
    if (!$input->isValid('id') || $input->id < 0) {
      throw new Zend_Exception('Invalid ID provided');
    }

    $this->_id = (int) $input->id;
    return $this;
  }

  /**
   * getId()
   *
   * Gets the ID of the Client Model
   *
   * @access public
   * @return integer
   */
  public function getId()
  {
    return $this->_id;
  }

  /**
   * setName()
   *
   * Sets the name of the model
   *
   * @access public
   * @return Application_Model_Client
   */
  public function setName($arg)
  {
    $input = new Zend_Filter_Input($this->_filters, $this->_validators);
    $input->setData(array('name'=>$arg));
    if (!$input->isValid('name') || is_numeric($input->name)) {
      throw new Zend_Exception('Invalid NAME provided');
    }
    $this->_name = (string) $input->getUnescaped('name');
    return $this;
  }

  /**
   * getName()
   *
   * Returns the name of the client
   *
   * @access public
   * @return string || null
   */
  public function getName()
  {
    return $this->_name;
  }

  /**
   * setDescription()
   *
   * Sets the description of the client
   *
   * @access public
   * @return Application_Model_Client
   */
  public function setDescription($arg)
  {
    $input = new Zend_Filter_Input($this->_filters, $this->_validators);
    $input->setData(array('description'=>$arg));
    if (!$input->isValid('description')) {
      throw new Zend_Exception('Invalid DESCRIPTION provided');
    }
    $this->_description = (string) $input->getUnescaped('description');
    return $this;
  }

  /**
   * getDescription()
   *
   * Returns the description of the client
   *
   * @access public
   * @return string || null
   */
  public function getDescription()
  {
    return $this->_description;
  }

  /**
   * setFlagActive()
   *
   * Sets the active flag of the client
   *
   * @access public
   * @return Application_Model_Client
   */
  public function setFlagActive($arg)
  {
    $input = new Zend_Filter_Input($this->_filters, $this->_validators);
    $input->setData(array('flag_active'=>$arg));
    if (!$input->isValid('flag_active')) {
      throw new Zend_Exception("Invalid FLAG_ACTIVE provided\n".Zend_Debug::dump($input->getMessages()));
    }
    $this->_description = (string) $input->getUnescaped('flag_active');
    return $this;
  }

  /**
   * getFlagActive()
   *
   * Returns the active flag of the client
   *
   * @access public
   * @return bool || null
   */
  public function getFlagActive()
  {
    return $this->_flag_active;
  }

  /**
   * setFlagDeleted()
   *
   * Sets the deleted flag of the client
   *
   * @access public
   * @return Application_Model_Client
   */
  public function setFlagDeleted($arg)
  {
    $input = new Zend_Filter_Input($this->_filters, $this->_validators);
    $input->setData(array('flag_deleted'=>$arg));
    if (!$input->isValid('flag_deleted')) {
      throw new Zend_Exception("Invalid FLAG_DELETED provided\n".Zend_Debug::dump($input->getMessages()));
    }
    $this->_description = (string) $input->getUnescaped('flag_deleted');
    return $this;
  }

  /**
   * getFlagDeleted()
   *
   * Returns the deleted flag of the client
   *
   * @access public
   * @return bool || null
   */
  public function getFlagDeleted()
  {
    return $this->_flag_deleted;
  }

  /**
   * populate()
   *
   * Populates the model with specified attributes
   *
   * @access  public
   * @param   ArrayObject || array $data Data to be populated
   * @return  Application_Model_Client
   */
  public function populate($data)
  {
    if (is_array($data)) {
      $data = new ArrayObject($data, ArrayObject::ARRAY_AS_PROPS);
    }

    if (isset($data->id))           $this->setId($data->id);
    if (isset($data->name))         $this->setName($data->name);
    if (isset($data->description))  $this->setDescription($data->description);
    if (isset($data->flag_active))  $this->setFlagActive($data->flag_active);
    if (isset($data->flag_deleted)) $this->setFlagDeleted($data->flag_deleted);
  }

  /**
   * toArray()
   *
   * Returns the objects data as an array
   *
   * @access public
   * @return array
   */
  public function toArray()
  {
    return array(
      'id'            => $this->getId(),
      'name'          => $this->getName(),
      'description'   => $this->getDescription(),
      'flag_active'   => $this->getFlagActive(),
      'flag_deleted'  => $this->getFlagDeleted()
    );
  }

//endregion
}