Sorry I'm late to the party, but thought it might still be useful to add my 2 cents...
I can confirm with certainty that the TESTING... output, including TESTING ENTERNET, simply did not appear at all in the boot sequence until I hunted down and used the apparently magical ADB0036 adapter.
Initially, I was using another, apparently functional adapter that displayed the boot process and allowed me to interact with it to boot to single user. One would normally expect that would be good enough for the whole boot process, right? Wrong! If you want to see the boot menu, you need the ADB0036, or equivalent.
If you get in a pinch and need to get at the boot menu, don't have an ADB0036 adapter and are up for building your own, there are wiring diagrams out on the net.
-cw-