Mockbin : Mockbin allows you to generate custom endpoints to test, mock, and track HTTP requests & responses between libraries, sockets and APIs.
httpbin.org : A simple HTTP Request & Response Service.
Vcr : Record your test suite's HTTP interactions and replay them during future test runs for fast, deterministic, accurate tests.
Siege : Siege is an http load testing and benchmarking utility. It was designed to let web developers measure their code under duress, to see how it will stan...
Mock Service Worker : Mock by intercepting requests on the network level. Seamlessly reuse the same mock definition for testing, development, and debugging.
Smocker (server mock) is a simple and efficient HTTP mock server. Smocker exposes a configuration user interface and a configuration api to register new mocks.