Indeed it’s a very tricky subject!
The real issue here is: we still don’t understand what consciousness is, and how it originates.
There are many theories from philosophy, psychology, neuroscience, but none is clear and easily applicable to a software.
Until now, the best solution I’ve seen is what I call “the one way soultion”: it doesn’t matter whether the machine has consciousness or not.
What matters is that the user, the human being who interacts with the machine, perceives it as human.
It works, as replicating the human behaviour is becoming more and more easy and accurate.