Describe bottom-up and top-down approaches in Regression Testing.

Describe bottom-up and top-down approaches in Regression Testing.

Bottom-up approach : In this approach testing is conducted from sub module to main module, if the main module is not developed a temporary program called DRIVERS is used to simulate the main module.

Top-down approach : In this approach testing is conducted from main module to sub module. if the sub module is not developed a temporary program called STUB is used for simulate the submodule.