spree/spree — comment on commit 9fab32e987194898aedd7b750a9d18a9c9b69551
File:  line 0
By radar:

on_hand is automatically converted to an integer in the model: https://github.com/spree/spree/blob/master/core/app/models/spree/variant.rb#L36. This means the last test in this commit will fail, as it will be valid.

You may want to consider removing this conversion and then re-adding the validation.