I had troubles while running tests on Active Record:
bundle exec rake test_sqlite3
/Users/oscardelben/code/rails/activesupport/lib/active_support/core_ext/hash/keys.rb:70:in `block in assert_valid_keys’: Unknown key: extend (ArgumentError)
This is because some models used by tests are using the extend option which now seems deprecated.
Should related tests be removed/migrated to not use these options anymore?
I don’t see mentions in the Changelog and documentation, but if this is the right direction I’d volunteer to update the code and docs.