Stubs Replacements for missing components that the components being tested will call as part of the test by sevy While doing an Integration , If we don't have all the modules get ready and Need to test a particular module which is ready then We Use Stubs and Drivers. Stubs and drivers used in Integration testing for a Top Down Integration testing and Bottom Up Integration Testing.
For Example you have 3 modules say A, B and C in your application. The A and C is ready but the bridge between A to C is B is not ready so how you can test the whole system A, B and C together. Here you need to use some dummy system which would take the input and pass it to C. It is not the complete B system but still will serve the purpose to have a path between A and C. This is called stub and driver.