Quote by Barbara Liskov
"A specification should be testable; if you cannot test it, you cannot claim to have specified it."
More from Barbara Liskov
"The key to good software design is understanding the problem domain deeply before writing code."
"Abstraction is not about being vague; it's about capturing the essential complexity while hiding the irrelevant details."
"A program should be written for people to read, and only incidentally for machines to execute."
"Good design is about making trade-offs consciously, not accidentally."