In computer science it is often assumed that a human mind can be reduced to a Turing machine.
Since when? I've read a lot of computer science papers and never once encountered this assumption.
This is the assumption that underlies the field of artificial intelligence.
Not really. I think artificial intelligence can exist independently of the ability to emulate human intelligence. Deep Blue beat Kasparov, and we're pretty sure it didn't do it by emulating human thought processes.
However, it is an assumption, one that has neither been proven or disproven. Is there any kind of test within our current capabilities where we can prove/disprove this assumption?
I personally suspect the assumption is true. I think it could only be proven by constructing a computer simulation of a particular human's brain and asking a series of questions, both of the human and of the simulated version, and seeing if the answers are indicative of a similar level of skill and knowledge. I would not expect the answers to be identical, even if the simulation is highly accurate. Constructing a computer simulation of a human brain is not remotely feasible at present.
If not, is there any evidence that would suggest one way or another?
With accurate equations, we expect a TM to be, in principle, capable of simulating any physical system, including in particular a human brain. The hard parts are (1) having correct quantum mechanics equations and (2) data acquisition of the initial state of a human brain. While these are not feasible today, there's no reason to believe they cannot be done in principle. Note we assume human thought is "reducible" to a TM even if the simulated brain is way slower than a real brain.