1. A test support program executed by a computer for performing an operational test of a program under development by using test patterns each of which includes a parameter to be inputted to a function defined in the program under development and a return value to be outputted from the function, said test support program makes said computer perform processing comprising the steps of: (a) acquiring a post-update operation description which defines details of an operation of a function included in said program under development after an update when said program under development undergoes the update; (b) selecting a pre-update operation description which has high commonality with said post-update operation description acquired in step (a), from among a plurality of pre-update operation descriptions defining details of operations of functions included in said program under development before the update; (c) extracting a pre-update test pattern for an operational test of said pre-update operation description selected in step (b), from among a plurality of pre-update test patterns prepared for operational tests of the program under development before the update; and (d) generating a post-update test pattern for an operational test of said post-update operation description acquired in step (a), by inheriting at least a portion of said pre-update test pattern extracted in step (c).