Integration Testing Approaches:
1. Big Bang: Where all of the modules are combined together and tested as single system. In this approach tester test only data flow between integrated parts not the entire system as happened in the system testing.
2. Top Down: In this approach top level modules (units) are tested before and then the lower level modules (units) step by step. Generally we follow this approach if top down model is used for development as well.There Stubs are used to simulate lower level module to test top level module if lower level module that may not be implemented in the initial phase.
3. Bottom Up: In this approach bottom level modules (units) are tested before the upper level modules (units) and step by step bottom to up.We follow this approach if bottom to up approach is also followed in development as well. There Drivers are used to simulate upper level module to test lower level module that may not be available during the initial phase.
4.Sandwich/Hybrid: The approach where we combined Top Down and Button Up approaches to perform integration testing.