cosmos-sdk/x/ibc/testing/mock/README.md

This package is only intended to be used for testing core IBC. In order to maintain secure testing, we need to do message passing and execution which requires connecting an IBC application module that fulfills all the callbacks. We cannot connect to ibc-transfer which does not support all channel types so instead we create a mock application module which does nothing. It simply return nil in all cases so no error ever occurs. It is intended to be as minimal and lightweight as possible and should never import simapp.