mswjs / msw

The industry standard for API mocking in JavaScript.

SpectoLabs / hoverfly

Lightweight service virtualization/ API simulation / API mocking tool for developers and testers

dotnet / dev-proxy

Simulate API failures, throttling, and chaos — all from your command line.

Pikopod / pikopod

A sandbox for the third-party APIs you depend on. Built from the provider's spec, it fails on purpose, and it replays the exact failure production hit.