A proof of correctness is much more valuable than 1000 test (if that proves correct) since it guarantees that the program will work correctly for all possible inputs.
Us roz, us saal, us Kshan Aisa laga ki Banaras ki saari bhaang hamare mathe mai, aur bholenaath ka saara zahar hamari aankhon Mai uttar aya ho.
~ Raanjhanaa
What will you give
When death knocks at your door ?
The fullness of my life-
The sweet wine of autumn days and summer nights,
My little hoard gleaned through the years,
And hours rich with living.
These will be my gifts,
When death knocks at my door.
- Tagore