WireMock.Net

Free and Open Source tool for building mock APIs. Create stable development environments, isolate yourself from flakey 3rd parties and simulate APIs that don't exist yet. WireMock frees you from dependency on unstable APIs and allows you to develop with confidence. It's easy to launch a mock API server and simulate a host of real-world scenarios and APIs - including REST, SOAP, OAuth2 and more. WireMock is a free API mocking tool that can be run as a standalone server, or in a hosted version via the WireMock Cloud-managed service. API mocking involves creating a simple simulation of an API, accepting the same types of request and returning identically structured responses as the real thing, enabling fast and reliable development and testing.