How Do You Justify Test Driven Development?

On test driven development, opinions vary So let me give you some advice for the wary Performance? It’s easy as to convey You can run some numbers and see what they say UX? It’s subtle but quick to effect And you’ll get lotsa smiles from the users you met Following a style guide and conveying intent? You’ll see straight away mismatching indents! But how do you teach how it feels to be free Of staying back late to fix bug 93? How do you convey in actual words When the software you write actually actually works?