Testies at the start of a salesletter have more to do with "greasing the proof".
For example, you're about to make a big claim in your headline, deck copy, or lead.
Here's an example of what I mean:
How To Beef Up Your Proof - Part 2 | A Prescription in Marketing
In this case, the testies are "warming them up" for what you're about to reveal.
I certainly didn't invent that. But it appears to work, in my (admittedly) limited tests.
Perhaps Michel or some others can weigh in on more definitive testing they've done, if they care to share their results.
But I learned that technique from Gary Halbert years ago.
Saw it again later (was it Schwartz? Or Hopkins? Can't recall at the moment)
So it's pretty established.
Now if I can just get those testies to mold to my copy!
EDIT: It was Schwartz! Geez, had to read my own blog comments to remember. Man, I'm getting old!