The article has the answer to your question: There was no lens, just a pinhole. The lens and filter system gets integrated "over the next few months". They tested the sensor array, not the lens.
Ha, that's how I tested a DSLR that I had repaired. There was no matching objective there, so I wrapped aluminium foil over the front and, using a needle, stabbed a tiny hole into it. The pinhole setup was good enough to test what I needed to test :D
