Inspired by Danny Sipos's (Upchuk) article: https://www.webomelette.com/simple-guzzle-api-mocking-functional-testing...

Problem

When running tests, you don't want to perform external HTTP requests while you still want to test code that consumes such webservices. This module intercepts the requests made by the Drupal http_client service and allows a plugin to respond with a mocked response.