That prototyping later becomes extremely useful for building local databases -- a strong factory suite means I can rebuild my local database and have it completely populated with randomized dummy data. Changing locales on some packages means I can have a local environment populated with data tailored for a completely different country and language, for example.
Re: surfacing bugs -- in a lot of cases yes. And a lot of bugs have been found this way.
If a developer can test, that's a good fundamental skill. If they don't use a factory, that says nothing about their fundamentals – it's something you can easily tell someone who knows how to test to go learn & do once they're on the job.
If taking an extra an hour of time to sell your work is "throwaway" then that person is either shotgun applying to jobs (and not being hired for a reason) or they're not taking their application seriously.
Think about it this way. It takes about 2 hours to learn how to write unit tests for someone who has never done it. Why make something as trivial so important in your interview process? I understand unit tests are important, but they aren't difficult.
If it's really that trivial, the developer should be doing it so routinely that it should take less than 15 minutes to write unit tests for the take home exercise. Your statement literally demolishes any excuse for not doing it.
All too well, my friend. That is why the employer is justified in asking for a demonstration of the ability to write good unit tests, as you have demonstrated by your own admission.
According to him, if I didn't setup a factory, when doing a take home assignment, then I'm not competent to write unit tests. I disagree.
So many people interview poorly. It's gotten worse every time I read about it. They're pushing away talent that way. I know people are stuck in their ways, but it's a bad idea unless you are are just looking for juniors and people desperate enough to go through that. I'm neither.
I mean don't people realize it's a seller's market?
Why? That seems like an oddly specific thing to be a _huge_ red flag. Are you expecting random data to actually surface bugs - ie: making your tests non-deterministic? Or is there some other benefit you are looking for to make it such an important criteria?