"I'm surprised that you do not understand ... I'd expect a developer to know what unit tests are and to have done this for all your code in the past".
That statement is simply rubbish. Most developers know what unit tests are but not everyone unit tests their code. I'd just say that the guy has a bee in his bonnet about unit testing. He thinks its the best thing since sliced bread and everyone should do it.
Unit testing is still fairly new in my opinion. More and more people are taking it up but its not as popular as this guy seems to think. No doubt some people have been doing it for years but I'd say more just don't.
Another case of a little knowledge can be dangerous I think.
Personally, unless your company procedures call for including unit testing when you write code then I wouldn't worry about it.
Nobody mentioned unit tests, and nothing in the processes documentation mentioned it (I am a contractor); it was brought up just before deployment after 4 months of coding. Of course, I believe that testing should happen as soon as possible for each bit, but they want "sign off" on ALL the test cases "before QA is involved".