From the slightly-odd The Way of Testivus, via InfoQ:
The pupil asked the master programmer:
“When can I stop writing tests?”The master answered:
“When you stop writing code.”The pupil asked:
“When do I stop writing code?”The master answered:
“When you become a manager.”The pupil trembled and asked:
“When do I become a manager?”The master answered:
“When you stop writing tests.”The pupil rushed to write some tests.
He left skid marks.If the code deserves to be written,
it deserves to have tests.