Albert Barnes on Ephesians 5:10

Proving what is acceptable unto the Lord. That is, "Walk as children of light, Eph 5:8, thus showing what is acceptable to the Lord." Rosenmuller supposes that the participle is used here instead of the imperative. The meaning is, that by so living you will make a fair trial of what is acceptable to the Lord. The result on your happiness, in this life and the next, will be such as to show that such a course is pleasing in his sight. Dr. Chandler, however, renders it as meaning that by this course they would show that they discerned and approved of what was acceptable to the Lord. Rom 12:2, where a similar form of expression occurs.

(h) "what is acceptable" Rom 12:2