Purpose Of Integration Testing

The purpose of integration testing is to verify functional, performance and reliability requirements placed on major design items. These "design items", i.e. assemblages (or groups of units), are exercised through their interfaces using black box testing, success and error cases being simulated via appropriate parameter and data inputs. Simulated usage of shared data areas and inter-process communication is tested and individual subsystems are exercised through their input
interface. Test cases are constructed to test that all components within assemblages interact correctly,
for example across procedure calls or process activations, and
this is done after testing individual modules, i.e. unit testing.