I wear a green wrist-band that says “Test First”. This green band is a symbol of my committment to a minimum standard of professional behavior. Part of that minimum standard is: “I will not release code that I have not tested.”
A committment like this changes the sense of the decision you referred to above. Testing becomes a discipline, not a trade-off, a committment to professional behavior, as opposed to a convenience.
When we accept that writing unit tests first is simply part of standard professional behavior, then the quandry of whether it takes too much time or not will diminish.