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SpectoLabs

SpectoLabs/hoverfly

Open-source API simulation and mocking tool that lets developers and testers replace flaky or slow API dependencies with reusable simulations.

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What is it?

Hoverfly creates realistic simulations of the APIs an application depends on. Teams use it to swap out slow, unreliable or costly external services during development and testing, so tests run against predictable responses.

Beyond static mocks, Hoverfly can inject network latency, random failures and rate limits to exercise edge cases. Simulations can be exported, shared, edited and imported, and the tool is controlled through a CLI and a REST API. Java bindings are available, and the project describes extending behaviour with any programming language.

Hoverfly is written in Go, distributed as a lightweight binary that runs on a range of platforms, and licensed under Apache 2.0. It is developed and maintained by iOCO Solutions.

Key features

  • 01Create reusable API simulations that can be exported, shared and imported.
  • 02Inject network latency, random failures and rate limits to test edge cases.
  • 03Control the tool through a CLI and a REST API.
  • 04Provides native Java language bindings.
  • 05Lightweight Go binary that runs on multiple platforms.

Use cases

  • Replacing slow or unreliable third-party APIs in integration tests.
  • Simulating rate limits or failures to verify how an application handles errors.
  • Developing a frontend or service before its backend dependencies are ready.

Quick start

  1. 1

    Install Go from the official website

  2. 2

    Clone the Hoverfly repository

    git clone https://github.com/SpectoLabs/hoverfly.git
  3. 3

    Build the binaries from the project directory

    cd hoverfly && make build

Things to know

  • Setup for building from source requires Go and make, and binaries are placed in the target directory.
  • Some middleware tests need Ruby and Python installed.

In collections

Testing frameworks & test automation tools

Topics

#api-mocking#service-virtualization#testing#http#proxy#golang#api-mock#api-simulation#go#hoverfly

FAQ

What is hoverfly?
Open-source API simulation and mocking tool that lets developers and testers replace flaky or slow API dependencies with reusable simulations. Hoverfly creates realistic simulations of the APIs an application depends on. Teams use it to swap out slow, unreliable or costly external services during development and testing, so tests run against predictable responses.
Is hoverfly free to use? What license does it have?
hoverfly is open source under the Apache-2.0 license. Check the license terms before using it in commercial products.
Is hoverfly still maintained?
Actively maintained. The last commit to hoverfly was on Oct 21, 2026.
What can I use hoverfly for?
Replacing slow or unreliable third-party APIs in integration tests. Simulating rate limits or failures to verify how an application handles errors. Developing a frontend or service before its backend dependencies are ready.
How do I install hoverfly?
Install Go from the official website Clone the Hoverfly repository: git clone https://github.com/SpectoLabs/hoverfly.git Build the binaries from the project directory: cd hoverfly && make build
Where can I get hoverfly?
The source code and installation instructions are on GitHub: https://github.com/SpectoLabs/hoverfly

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