Top-Down & Bottom-Up Testing.
1 Answer
Sr. No Top down testing Bottom up testing
1. Top-down integration testing is an integration testing technique used in order to simulate the behaviour of the lower-level modules that are not yet integrated. Stubs are the modules that act as temporary replacement for a called module and give the same output as that of the actual product. Bottom up integration testing also uses test drivers to drive and pass appropriate data to the lower level modules. As and when the code for the other module gets ready, these drivers are replaced with the actual module.
2 Advantageous if major flaws occur toward the top of the program. Advantageous if major flaws occur towards the bottom of the program.
3 In top down approach, main() function is written first and all sub functions are called from main function. Then, sub functions are written based on the requirement. In bottom up approach, code is developed for modules and then these modules are integrated with main() function.
4 Top down approach begins with high level design and ends with low level design or development. Bottom up approach begins with low level design or development and ends with high level design.
5 Structure/procedure oriented programming languages like C programming language follows top down approach. Object oriented programming languages like C++ and Java programming language follows bottom up approach.
6 Top-down approach analyzes risk by aggregating the impact of internal operational failures Bottom-up approach analyzes the risks in individual process using models
7 Top-down approach doesn’t differentiate between high frequency low severity and low frequency high severity events Bottom-up approach does differentiate between high frequency low severity and low frequency high severity events
8 Top-down approach is simple and not data intensive Bottom-up approach is complex as well as very data intensive
9 Top-down approaches are backward-looking Bottom-up approaches are forward-looking
10 Top Down --> BIG SYSTEM to smaller components Bottom Up --> smaller components to BIG SYSTEM
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