Solanum integrifolium Photo shows the fruit -- about the size of lemons. The plant is otherwise identical in growth and appearance of eggplant (Solanum melongena).
Solanum quitoense - this is a prickly form of naranjilla, and probably misidentified.
This is an interesting foliage plant with its red-veined leaves and murderous looking spines on both leaves and stems. The spines are quite soft however, and cause no problem as they cannot leave the plant. I suppose that lizards and snakes will stay well clear of it though. The pink buds open into insignificant white flowers which are followed by golf-ball size seed pods with a fuzzy coating. It requires a long growing season if the fruit is to mature in zone 5a -- start the seeds early.