What is Sandwich testing?

Sandwich testing is a type of testing that consist of two parts,they are Top-down approach and Bottom-up approach.It combines the advantages of both Bottom-up testing and Top-down testing at a time.Bottom-up testing starts from middle layer and goes upward to the top layer where as Top-down testing starts from middle layer and goes downward. Big-bang approach is followed for the middle layer. From this layer bottom-up approach goes upwards and top-down approach goes downwards.

Advantages of Sandwich Testing

• Sandwich approach is useful for very large projects having several subprojects.When development follows a spiral model and the modul itself is as large as a system, then one can use sandwich testing.
• Both Top-down and Bottom-up approach starts at a time as per development schedule. Units are tested and brought together to make a system .Integration is done downwards.
• It needs more resources and big teams perform both bottom-up and top-down methods of testing at a time or one after the other.

Disadvantages of Sandwich Testing

• It require very high cost for testing because one part has Top-down approach while another part has bottom-up approach.
• It cannot be used for smaller system with huge interdependence between different modules.It makes sense when the individual subsystem is as good as complete system.
• Different skill sets are required for tester at different level as module are separate system handling separate domains like ERP products with modules representing different functional areas.

Hope this article helps you to understand Sandwich testing.