You can turn on all validations by using the Doctrine_Core::VALIDATE_ALL attribute with the following code:
// bootstrap.php
// ...
$manager->setAttribute(Doctrine_Core::ATTR_VALIDATE, Doctrine_Core::VALIDATE_ALL);
You can also configure Doctrine to validate lengths and types, but not constraints with the following code:
// bootstrap.php
// ...
$manager->setAttribute(Doctrine_Core::ATTR_VALIDATE,
Doctrine_Core::VALIDATE_LENGTHS | Doctrine_Core::VALIDATE_TYPES);