Explain Incremental Approach?

Answer

In this approach, testing is done by joining two or more modules that are logically related. Then the other related modules are added and tested for the proper functioning. Process continues until all of the modules are joined and tested successfully.

This process is carried out by using dummy programs called Stubs and Drivers. Stubs and Drivers do not implement the entire programming logic of the software module but just simulate data communication with the calling module.

Stub: Is called by the Module under Test.

Driver: Calls the Module to be tested.

Incremental Approach in turn is carried out by two different Methods:

• Bottom Up
• Top Down

Bottom up Integration

In the bottom up strategy, each module at lower levels is tested with higher modules until all modules are tested. It takes help of Drivers for testing

Advantages:

• Fault localization is easier.
• No time  is wasted waiting for all modules to be developed unlike Big-bang approach

Disadvantages:

• Critical modules (at the top level of software architecture) which control the flow of application are tested last and may be prone to defects.
• Early prototype is not possible

Top down Integration:

In Top to down approach, testing takes place from top to down following the control flow of the software system.

Takes help of stubs for testing.

Disadvantages:

• Needs many Stubs.
• Modules at lower level are tested inadequately.