You can validate default values as you enter them. The Designer includes a Validate button so you can ensure valid default values. A message appears indicating if the default is valid.
The Designer also validates default values when you save a mapping. If you enter an invalid default value, the Designer marks the mapping as not valid.
The Developer tool validates default values as you enter them.
The Developer tool validates default values when you save a mapping. If you enter a default value that is not valid, the Developer tool marks the mapping as not valid.