> So does this mean that neither did the original utils have any test harness, the process of rewriting them didn't start by creating one either?

Yes.

> Sure there are many edge cases, but surely the OS and FS can just be abstracted away and you can verify that "rm .//" actually ends up doing what is expected (Such as not deleting the current directory)?

I think people have been trying that since before I was born and haven't yet been successful, so I am much less sure than you are.

For example: How do you decide how many `/` characters to try?

For a better one: Can you imagine if "rm" could simply decide to refuse to delete files containing "important" as first 9 bytes? How would you think of a test for something like that without knowing the letters in that order? What if the magic word wasn't in a dictionary?

> This doesn't seem like sloppy coding, nor a critique of the language, it's just the same old "Oh, this is systems programming, we don't do tests"?

I've never heard anyone say that except as a straw man.

I've heard people say tests don't do what people think they do.