Hoverfly vs mountebank

Hoverfly Cloud is a hosted API simulation and mocking platform for testing without live API dependencies. It handles HTTP/S services including REST, SOAP, XML, JSON, and GraphQL. Users can capture and replay traffic, generate simulations from OpenAPI specifications, and match requests by methods, headers, parameters, and bodies. Simulations can delay responses, inject faults or errors, and modify replies. A command-line interface supports scripted configuration and testing pipelines. Hoverfly and hoverctl binaries run on macOS, Linux, and Windows, while documentation covers Docker and Kubernetes installation. The underlying Hoverfly framework is open source under Apache 2, has no GUI, and is generally run locally or in a user’s infrastructure. Cloud use cases include performance testing, functional testing, and development.

mountebank is a free, self-hosted service-virtualization tool that supplies test doubles instead of real application dependencies. Through its HTTP API, developers configure stubs, record and replay proxies, and verify mock expectations. HTTP, HTTPS, TCP, and SMTP are built in; community plugins add LDAP, WebSockets, GraphQL, SNMP, Telnet, SSH, and NETCONF. Installation documentation covers npm and Docker. Community extensions list client libraries for C#, Clojure, Go, Java, JavaScript, Python, Ruby, TypeScript, and Swift, along with Grunt, Gradle, and Maven plugins. Stateful simulation, fault injection, and record-and-replay are supported. By default, mountebank stores everything in memory, which its site says can become a performance bottleneck at scale. Security guidance warns that JavaScript injection can permit code execution on the machine and recommends localhost-only access or an IP whitelist. CORS is disabled by default, and safe origins can be enabled explicitly.