My team built a new JS framework for mocking REST APIs called "unmock" that focuses on fuzz testing integrations. We hope to move it closer to property-based testing libraries like fast-check. The hard part is building a shrinker - shrinkers (https://medium.com/criteo-labs/introduction-to-property-base...) are tough to get right when testing side effects. Please check out the article, leave your feedback if any, try out unmock (https://github.com/Meeshkan/unmock-js) and let me know what you think!