mountebank

mountebank is the first open source tool for cross-platform, multi-protocol test doubles over the wire. It supports HTTP, HTTPS, TCP (text and binary), and SMTP protocols. Current stable version is 2.9.4, published under the @mbtest/mountebank package (was formerly mountebank). The community-driven project requires Node.js >=20. It offers mock verification, stubbing with advanced predicates, JavaScript injection, and record-playback through proxying, distinguishing itself from alternatives like WireMock by supporting multiple protocols and being fully open source without platform constraints. Releases are maintained by the mountebank-testing organization.