I think the tests like this could be rewritten much more simply as:
```ruby
should validate_presence_of(:version_number)
```

http://rdoc.info/gems/shoulda-matchers/Shoulda/Matchers/ActiveModel#validate_presence_of-instance_method
"shoulda-matchers" is already available via "shoulda".

See, for example:
https://github.com/alphagov/support/blob/master/test/unit/models/campaign_request_test.rb#L4