class AppModel extends Model{

	function validates($validationVar = 'validate') {

		// copy the data over
		if ($validationVar != 'validate') {
			$temp = $this->validate;
			$this->validate = $this->{$validationVar};
		}
		$errors = $this->invalidFields();

		// copy it back
		if ($validationVar != 'validate') {
			$this->validate = $temp;
		}
		if (is_array($errors)) {
			return count($errors) === 0;
		}
		return $errors;
	}
}

// assuming this was in my model:
var $justTesting = array(
	'name'	=> array('rule'=>array('minLength', '1'), 'required'=>true, 'message'=> 'CRRRRAAAZZZY!'),
	);

// I could test against that rule from my controller using:
$this->ModelName->validates('justTesting');
pr($this->ModelName->validationErrors);