vercel-labs/emulate [1], has stripe and twilio (their emulators are much more shallow generally like their AWS one can't really be compared to floci here, but i've made custom ones for stuff like emulating hardware devices (airplay/google play) with much success so you can basically extend their base framework with custom emulators or their own provided ones to your needs on a fork.

1. https://github.com/vercel-labs/emulate

for modelling and testing a CI software i was working on, i had to extend their github emulator in several places for example. but it was great to already have a working base.