What sort of tests did the L85A1 undergo before being adopted?

Aug 2016
I've heard the L85 was a dumpster-fire from the start, and it was particularly bad in Desert Storm. So bad in fact, the British had to hire the Germans (Heckler and Koch) to fix its problems. Admittedly, the company was owned by the British at the time.

Anyway, I'm curious what sorts of tests were performed with the rifle prior to it's adoption. How did a rifle that bad become adopted in the first place?