I believe it to be much better to see a candidate write some code quickly, have them write unit tests for it, discover that some cases were not handled properly

I believe it to be much better to see a candidate write some code quickly, have them write unit tests for it, discover that some cases were not handled properly and then they were. This is how 99% of developers work, I don't believe anyone who says they write their code perfectly and under stress every single time.