Object#with introduced by Rails 7 didn’t play nice with minitest-substitute until now. I’ve therefore dropped the the conflicting “with” on the new minitest-substitute-1.0.0 release in favour of “substitute” to override variables of any kind for the duration of a block in your tests or specs. https://github.com/svoop/minitest-substitute?tab=readme-ov-file#update-from-0xx-to-1xx