Your friend doesn't know how to use the tester. A tester can be fooled into a false positive reading when a wire that's not connected to anything couples stray voltage from adjacent wiring. It won't be enough current to light a bulb or even give you a perceptible shock when you touch it.

You need competent help. If you check all the breakers and fuses and they are OK, check to see if there is another light switch that is supposed to be feeding the same light. Try flipping that a few times (in different combinations of the first switch you found) to see if that makes a difference.
Look around the kitchen, bathrooms, garage, and outside for GFCI's that may be tripped. While the lighting shouldn't be on such a circuit, stranger things have happened.

If none of the easy stuff works, someone who knows how to use a meter properly will need to star tracing things.

What do you think about changing out the entire light source itself?

If you don't have power to the present fixture, changing the fixture will not change the underlying problem.

No there is power to it

If you do have power to the light but no light (and you know the light bulb is good) my first guess, absent the proper test equipment, would be that the socket isn't making good contact with the bulb. At the bottom of the socket there's a little tab and over time it can get bent down. Take a heavy duty paper clip and straighten it out. With a pair of pliers bend a little right angle hook at the end of it, about 1/4" long. Ensure the power is OFF. Slip the hook behind the tab and pull it gently out so that the tab is at about a 45 degree angle to the bottom of the socket. Try the bulb.

If that doesn't work, you'll need some test equipment. Report back and we'll help you pick the right tools.

Will do. I will try that (with the breaker off of course). Thank you.