A control unit of a plant facilities testing apparatus implements a first step of obtaining unupdated screen information and updated screen information, a second step of obtaining an unupdated test-item table file, a third step of comparing the unupdated screen information with the updated screen information and extracting a change item and an addition item while categorizing a difference thereinto, a fourth step of creating a test-item table file for an addition portion based on the addition item, a fifth step of creating a test-item table file for a change portion based on the change item and the unupdated test-item table file, and a sixth step of creating an updated test-item table file by combining the test-item table file for an addition portion with the test-item table file for a change portion.
