[10ren]

I thought of another way to say this (not that you need it):

Sometimes you write code to throw away. James Gosling has said he does this. Fred Brooks said "build one to throw away". Novelists write drafts, artists draw sketches and sculptors carve studies (I was amazed to see that Michelangelo did several studies for his sculpture of David - full size, in marble!)

In contrast, tests are an investment in code. They make the code better, more reliable, more correct - more tested. They make it harder to throw away the code.