Just because a baby was made in a so called test tube, does not mean that they are any different that any other kid. They are still made from a sperm and and egg, just like the rest of us here on earth are, so yes they have a soul.
Test tube just means that they were started outside of the body. Test tube babies were still made from the same parts and are birthed the same. Thinking there is anything different or off about them is typically just the result of ignorance. Test tube babies are just the same as everyone else, they just got a little bit of a different start.
I would assume a test-tube baby has a soul. I believe a soul attaches to humans, so as long as a being fits that description then they must have a soul. Of course, that is assuming a soul exists at all for anyone. There's always the chance that they don't exist, since we can't prove them.
It seems to me irrelevant how a baby is conceived. Most theories about souls profess that the soul enters the body upon conception, other theories say at birth. I don't know of any theories that make it conditional upon the container the baby is conceived in, whether it be a uterus or a test tube. It doesn't even seem to be consistent with any biblical account of souls, so I suspect that a belief that test tube babies would not have souls is linked to a religious belief regarding the approved of method of conception - sex between a man and a woman.
Of course I do not think that a test tube baby's soul exists. I do not think souls exist at all. There is nothing besides the mechanical functioning of your nervous system, and there is no ectoplasmic soul that will rise from your carcass once you die--test tube baby, or otherwise.