It is said that “eternal vigilance is the price of liberty.”1 Yes, because eternal vigilance is the price of all quality. When writing code this means test as you go, test each key function immediately after it is written, not waiting until the entire program is written. CABTAB: code a bit ; test a bit . Early testing is probably the best idea ever for reducing coding errors . If we don’t catch the bugs in each code chunk as we write it, then later we will be less familiar with the code when we try to debug it.
We test for the expected output of known input. We test for out-of-range ...
