What is HoverFly?
HoverFly is a service virtualization tool that can emulate other services by recording requests and responses and then playing them back. It’s set as a proxy between your system and the services you want to emulate.
That way you can for instance test your system without using real dependencies, which increases the reliability of the tests.
When to use it
A service virtualization tool is often used as a complement or replacement for a mock or a stub. In my personal opinion, mocks work best when there are complex interactions with a few services and stubs are effective when there are simple