stretchr / testify

A toolkit with common assertions and mocks that plays nicely with the standard library

mockito / mockito

Most popular Mocking framework for unit tests written in Java

sinonjs / sinon

Test spies, stubs and mocks for JavaScript.

vektra / mockery

A mock code autogenerator for Go

hey-api / hey-api

👨‍🚀 Turn API specifications into production-ready SDKs, validators, mocks, and more. 20+ plugins. Millions of weekly npm downloads. Used by Vercel, OpenCode, PayPal, AWS, Autodesk, and many more.

mock-server / mockserver-monorepo

MockServer is an HTTP(S) mock server and proxy for testing that lets you mock APIs, inspect and modify live traffic, and inject failures. It supports HTTP/1.1, HTTP/2, gRPC, WebSockets, TCP and more on a single port, with additional support for HTTP/3, message brokers, and AI/LLM APIs.

nsubstitute / NSubstitute

A friendly substitute for .NET mocking libraries.

Kong / insomnia-mockbin

Insomnia Mockbin is the underlying backend for the API mocks capability of Insomnia. It is built and used by Kong, the author of the open-source Kong Gateway.

unkn0wn-root / resterm

Terminal API client for HTTP, GraphQL, gRPC, WebSocket and SSE. Plain .http files you can diff and version, with scripted tests, workflows, mocks, recorder, and a CLI runner for CI.

kubb-labs / kubb

🧡 Turn your API spec into type-safe code. Generate TypeScript types, API clients, hooks, validators and mocks from a spec such as OpenAPI.

TestableIO / System.IO.Abstractions

Just like System.Web.Abstractions, but for System.IO. Yay for testable IO access!

dashbitco / mox

Mocks and explicit contracts in Elixir

help-me-mom / ng-mocks

Angular testing library for mocking components, directives, pipes, services and facilitating TestBed setup

dwyl / aws-sdk-mock

:rainbow: AWSomocks for Javascript/Node.js aws-sdk tested, documented & maintained. Contributions welcome!

uber / mockolo

Efficient Mock Generator for Swift

steinfletcher / apitest

A simple and extensible behavioural testing library for Go. You can use api test to simplify REST API, HTTP handler and e2e tests.

pytest-dev / pyfakefs

Provides a fake file system that mocks the Python file system modules.

edgurgel / mimic

A mocking library for Elixir 🪎