mocking calls to specific addresses in solidity
Mocking a specific address signature in Solidity is useful for simulating expected behavior from an existing address or instance of a contract. In mock testing dependencies are replaced with simulated implementations to isolate the behavior of the funtion under test.
Proxy contracts that retain a specific address across deployments or general testing where implementation specific details are not relevant to the functions under test are both useful cases to employ a mock.
vm.mockCall enables you to return a value from a specific address and function signature in test code in Foundry
Full tutorial on YouTube: