Sandwich Testing
Sandwich testing is also called mixed testing.
Sandwich testing combines bottom-up testing and top-down integration testing. It is a kind of incremental testing strategy in which you test the top layers and bottom layers, and finally test the integrated system.
Steps to conduct Sandwich testing:
1. test the user interface in isolation, using stubs.
2. test the very lowest level functions, using drivers.
3. when the complete system is integrated, only the middle layer remains on which to perform the final set of tests. [Source of Steps]
Main disadvantage of Sandwich testing is that it does not test the individual subsystems thoroughly before integration.