Were you aiming for this? “Program testing can be used to show the presence of bugs, but never to show their absence!” ― Edsger W. Dijkstra

Or the second one, that I would have attributed to Dijkstra, too: “There are two ways of constructing a software design: One way is to make it so simple that there are obviously no deficiencies and the other way is to make it so complicated that there are no obvious deficiencies.” C.A.R. Hoare, The 1980 ACM Turing Award Lecture