I call this the rewrite fallacy. I honestly cannot think of a decent piece of work that I did that did not involve two three or a dozen rewrites - either from scratch (rare) or just piecemeal replacements until I reached a design I was happy with, that fit my domain and was appropriate.

Sometimes the rewrites were on the same project, sometimes the rewrites were on previous projects and I jus looked like a genius coming in to do something I had already done before , but I am always surprised if I can get things right first time (right enough is a professionals baseline, but actually right? Hardly ever).

So, no, I honestly think that thinking through a design, working out and testing out ideas and architectures is a necessary part of development - call it discovery, call it the first iteration, call it perfectionism, it's needed.

Tests should come as part of that. Slowly as you realise the approach you are choosin might actually be the right one and then increasingly as you fill out the space.