Model Validator tests

I need help with the Model Validator tests approach. Actually, this one is a very close to the core validator, and I don't know if I've done it well, or shall not be a validator. Anyway, I don't really know how to test this part in a good and unitary way.

Any idea, example, comment or help will be appreciated.

The first approach is setted in 428d9f2 but is just a "boilerplate"