"There's never an easy answer to the question "Should we do more testing?" because information can guide risk reduction, but doesn't necessarily do s… - Gerald M. Weinberg

"Testing may convincingly demonstrate the presence of bugs, but can never demonstrate their absence."- Edsger W. Dijkstra, Computing Pioneer (1930–2002), "Programming as a discipline of mathematical nature," Am. Math. Monthly, 81 (1974), No. 6, pp. 608–12.

If a program doesn’t work, measures of efficiency, of adaptability, or of cost of production have no meaning.

Fisher's Fundamental Theorem states — in terms appropriate to the present context — that the better adapted a system is to a particular environment, the less adaptable it is to new environments.