Testing after_commit with RSpec and mocking

I thought Mihail Davydenkov's comment deserved to be an answer:

You can also use subject.run_callbacks(:commit).

Also note that this issue (commit callbacks not getting called in transactional tests) should be fixed in rails 5.0+ so you may wish to make a note to remove any workarounds you may use in the meantime when you upgrade. See: https://github.com/rails/rails/pull/18458

Try to use test_after_commit gem

or add following code in spec/support/helpers/test_after_commit.rb - Gist