Modify the .ini file?   N-O.

Specify the name of an alternative ini file that is to be used for test purposes?   Perhaps.

Write a .pm module containing configuration information, with conditional logic therein?   Or, an outer, “wrapper” module which uses UNIVERSAL::require to choose from one of several?   Maybe better-yet.

A test might well use a different or modified environment/configuration, but it must not in any way alter the configuration, if only because those alterations would have to be tested too, ad infinitum.