Hoverfly

Hoverfly Cloud is a hosted service virtualization and API simulation platform built on Hoverfly Open Source, letting teams simulate the services their applications depend on, with a persistent journal, CORS support and authenticated instances on the paid tiers.

Keeping an open source core alongside a hosted product is the arrangement that makes adoption easy here, and it is the right shape for a developer tool. An engineer can install Hoverfly Open Source on a laptop and prove the idea works before anybody signs anything, and the hosted service exists for the point where simulations need to be shared across a team and survive a restart.

The persistent journal is the specific thing a laptop install cannot give you, because a record of every request a simulation served is what turns a debugging session into evidence, and it is exactly what disappears when a local process is killed.

Authenticated instances matter for a related and unglamorous reason: a simulation that anybody on the network can reach and modify is fine for one developer and unacceptable once a shared environment depends on it behaving predictably. Simulating latency and failure modes rather than only successful responses is the other reason a captured simulation beats a hand-written stub, since the interesting test is what the application does when a dependency times out. Hoverfly publishes plans from 10 dollars, with the open source core free to run locally.