I helping out on a test suite that came from Rails 4 (which I am not so familiar with) and there were some tests that had "with_after_commit: true" in their declaration.
After a bit of tinkering I removed it and the test suite ran a little bit faster.
It was used in rails_helper.rb as well, much like this: Why after_commit not running even with use_transactional_fixtures = false
The thing is: I can't find any information about it that would justify its use. I only find references to it in the thread above.
Thanks!
What you're looking for is the ActiveRecord callback called after_commit, not with_after_commit (this is just the name of your test case).
It's documented here and you can find plenty of resources if you just Google it.
It's also good to take a look at the Active Record Callbacks Guide.