It actually is a stub which resides within the server,

Actually during the test execution phase tests are running a self hosted controller available during the tests only.

It actually calls the mocked downstream over http, actual integration.

Not like mockito or something.

Actuall downstream call happens

It is like talking to yourself :-)

Helps in kinda UNIT testing mocking the downstream but without mockito.

coverage is also high.

Actually it is one of many examples - rightly said.

Though we can hang the response, mimic the downstream slow connection times etc.

Typically case to case base.

For tiny little microservices - consuming some other downstream - this can be helpful in specific