(My Distaste for) Coding Tests

I've been interviewing for about a month and as part of that process I was recently asked to do Fizzbuzz on a whiteboard and... it did not go well. I was not initially asked to do Fizzbuzz; I was asked how I would make it testable. The conversation went something like this:

Interviewer (I): How would you make Fizzbuzz testable?
Me: All code is inherently testable so I'm not sure I understand your question.
I: The way most people solve Fizzbuzz it is not testable. How would you do it differently?
Me: If the way most people solve Fizzbuz isn't testable then they're solving it wrong because - again - all code is inherently testable.
I: OK. Solve Fizzbuzz on the whiteboard.
Me: I'm not doing Fizzbuzz.
I: *perplexed look on his face* I just want you to show me how you would make Fizzbuzz testable.
Me: OK. *starts writing for loop on whiteboard and stops* I'm not going to write out a solution to Fizzbuzz. You'd basically make it testable by assigning the value ("Fizz", "Buzz", "Fizzbuzz", or the number) to a variable, injecting a logger class, and checking whether that logger class was called with particular parameters.
I: Can you be more specific?
Me: Not really. This isn't a difficult problem so it isn't a difficult solution.

As you can see, the interview got out of hand quickly. Since that day (about two weeks ago) I've been beating myself up for how everything happened and I've come to a few realizations that I want to share.

First and foremost, asking senior software engineers to solve a "problem" like Fizzbuzz is insulting. I have samples of my code freely available on Github and would gladly have written a small application on a computer to satisfy whatever coding requirements they have. Fizzbuzz is a test that should - at best - be given to developers who just finished school to see whether they can actually code.

I'm really conflicted on whether I think they should have just not asked me or I should have just answered. Ultimately, I think it's both. They shouldn't have asked that question, but when they did, I should have answered it. It wouldn't have been difficult to just write out a solution to Fizzbuzz on the whiteboard that was unit testable. I let me ego get the best of me ("You want me to do what?!") and it ended up costing me an opportunity.

Hopefully I've learned from this mistake and I won't react the same way in the future.