I don't think we need to have a global model and modify the global schema for this edge case. Please create a new `TestCase` in `timestamp_test.rb` using a similar setup like [this](https://github.com/rails/rails/blob/master/activerecord/test/cases/adapters/postgresql/hstore_test.rb#L8-L29). You can then define the table and the model inline and have it isolated to that test-case.