Integration testing in software testing

Integration Testing

•       Testing the Integration of multiple units / modules

–      The objective is to test the application that is built by integrating the unit tested components

–      This tests interfaces between components, interactions with different parts of a system such as O.S, hardware and interfaces between systems.

–      Testers should concentrate solely on integration itself and not functionality of the individual modules to be integrated.

•       Performed by the Developer / Tester

•       Various approaches to Integration Testing could be :

–      Top Down Integration (test control structures – compiling, loading and so on)

–      Bottom Up Integration (allows flexibility in scheduling and parallel testing)

–      Big Bang Integration (use controlled / restricted big bang; use it for backbone testing)

–      Sandwich Integration (use a combination of all)

v  Top Down Integration

–      An incremental approach to construction of program structure.

–      Modules are integrated by moving downward through the control hierarchy, beginning with the main control module.

–      The Integration process is performed in a series of five steps :

•       The main control module is used as a test driver and stubs are substituted for all components directly subordinate to the main control module.

•       Depending on the integration approach selected subordinate stubs are replaced one at a time with actual components.

•       Tests are conducted as each component is integrated.

•       On completion of each set of tests, another stub is replaced with the real component.

•       Regression testing may be conducted to ensure that new errors have not been introduced

v  Bottom-Up Integration

–      An approach that begins construction and testing with atomic modules (i.e. components at the lowest levels in the program structure).

–      Need for a stub is eliminated as the components subordinate that require processing is always available in this approach.

–      A Bottom-up integration strategy may be implemented with the following steps:

•       Low level components are combined into clusters that perform a specific software sub function.

•       A driver is written to coordinate test case input and output.

•       The cluster is tested.

•       Drivers are removed and clusters are combined moving upward in the program structure.

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