No need to read such a post...
Title says: "You don't inject for tests"
And, before opening the link, you know what you're going to find.
Someone confusing "testing" and "unit testing".
First thing that came to my mind (while reading the header on HN) was "There are several kind of testing..." but... Curiosity killed the cat. Let's open the link.
Ouch, first sentence:
"What is unit testing for?"
OK, closed.
Don't waste your time reading this crap ; )