[f. TEST v.2 + -ING2.] That tests or puts to the test or proof.
1847–8. H. Miller, First Impr., viii. (1857), 123. His writings … had stood their testing century but indifferently well.
1878. Gladstone, Glean. (1879), I. 179. I will add another and a very testing question.
1884. Pall Mall G., 13 Nov., 1/1. It is a testing crisis for English democracy.
1885. Beddoe, Races Brit., 271. An edifice of wood and stubble, which may … be consumed by the testing fire.
