Brian Kernighan: Code Testing and its Role in Teaching

"This report from the trenches focuses mainly on testing, with some digressions on topics that have led to useful class lessons. I am ignoring other important issues, like formal methods for both writing correct programs and for validating them after the fact. These are often of great value, but I am reminded of Don Knuth's apposite comment, "Beware of bugs in the above code; I have only proved it correct, not tried it." "
Read More >> http://www.cs.princeton.edu/~bwk/testing.html