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mountebank

mountebank is a free, self-hosted tool for developers who need applications to work against test doubles rather than real dependencies.

Place
#15 of 21
Score
5.8
mountebank's website

What mountebank is

mountebank is a free, self-hosted tool for developers who need applications to work against test doubles rather than real dependencies. Tests configure stubs, record and replay proxies, and check mock expectations through its HTTP API. HTTP, HTTPS, TCP, and SMTP are built in; community plugins add LDAP, WebSockets, GraphQL, SNMP, Telnet, SSH, and NETCONF. You can install it through npm or run a Docker image. Community extensions list client libraries for languages such as C#, Go, Java, JavaScript, Python, Ruby, and Swift, as well as build plugins for Grunt, Gradle, and Maven. It supports stateful simulation, fault injection, and record and replay. The default in-memory storage can become a performance bottleneck at scale. Security guidance warns that JavaScript injection can let attackers run code on the machine; it recommends protections such as localhost-only access or an IP whitelist. CORS is off by default, and safe origins can be enabled with a command-line flag.

Good

  • Free plan costs nothing.
  • Built-in support for HTTP, HTTPS, TCP, and SMTP.
  • Tests can record and replay proxies.
  • Client libraries cover multiple programming languages.
  • Install through npm or a Docker image.

Watch out

  • Default in-memory storage can bottleneck at scale.
  • JavaScript injection can allow code execution on the machine.
  • CORS is disabled by default.

Who it suits

mountebank suits developers who want to test applications using on-demand doubles for dependencies. Its multiple protocols and client libraries may fit teams using a range of languages and build tools.

Verdict

mountebank offers a free way to set up test doubles across several protocols, with plugins and client libraries for different development setups. Consider the in-memory storage limit and security guidance when planning its use.

Plans and prices

From mountebank's own pricing page, checked 4 Oct 2026.

All about pricing
PlanPriceWhat it gives you
FreeFreeOpen source service virtualization · No platform constraints stated

The facts

Each one read from mountebank's own pages, with the date it was checked.

What it does

API key option
The command-line documentation describes an optional API key that requires a matching x-api-key header for API requests.checked 4 Oct 2026
Audience
The site describes mountebank as a platform for developers to test applications against on-demand test doubles instead of real dependencies.checked 4 Oct 2026
Build integrations
Listed build tool plugins include Grunt, Gradle, and Maven.checked 4 Oct 2026
Built-in protocols
The site lists HTTP, HTTPS, TCP, and SMTP as built-in protocols.checked 4 Oct 2026
Client libraries
The community extensions page lists client libraries for languages including C#, Clojure, Go, Java, JavaScript, Python, Ruby, TypeScript, and Swift.checked 4 Oct 2026
Community protocols
The site lists LDAP, WebSockets, GraphQL, SNMP, Telnet, SSH, and NETCONF as community plugins.checked 4 Oct 2026
CORS
CORS is disabled by default to prevent CSRF attacks, and safe origins can be explicitly enabled with a command-line flag.checked 4 Oct 2026
Installation
The getting started guide documents installation through npm or running a Docker image.checked 4 Oct 2026
Persistence limit
By default, mountebank stores everything in memory; the page says this can become a performance bottleneck at scale.checked 4 Oct 2026
Purpose
mountebank provides cross-platform, multi-protocol test doubles over the wire for testing applications in place of real dependencies.checked 4 Oct 2026
Security
The security page warns that enabling JavaScript injection can allow attackers to run code on the machine and recommends protections such as localhost-only access or an IP whitelist.checked 4 Oct 2026
Support
The support page directs users to a Google group for help.checked 4 Oct 2026
Testing workflow
Tests use its HTTP API to set up stubs, record and replay proxies, and verify mock expectations.checked 4 Oct 2026

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