In an application currently in production, one module of code is being modified. Is it necessary to re-test the whole application or is it enough to just test functionality associated with that module?

It may not be necessary to test the whole application. Normally, Regression Testing techniques are implemented after the code is modified.

Actually speaking, a third person can’t comment on whether or not the whole application needs to be tested in the scenario mentioned by you.

You may test the whole module if
* the module is very small and any change in the code will reflect the entire module.
* previous attempts of not testing the whole module had proved expensive (Eg. client encountered errors or test team encountered a lot of errors in the rest of their testing process on the same/similar module).
* the developers suggest to do so.
* the client suggests/orders to do so.
* it is feasible (time and cost).

People involved in the project (SEPG) would know better about these points.

__________________
Lack of WILL POWER has caused more failure than
lack of INTELLIGENCE or ABILITY.

-sutnarcha-

Thanks, Sutnarcha,
satisfying explanation. I am new to this blog and trying to learn testing.

No, it's not necessary.It depends on application and fix/change performed.

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Brijesh Jain

You may want to test the added module once and run smoke test again to check if added functionality is not breaking or effecting the other functionalities