Holden (Auto) Viva - lost power and unsure of what next?

Hey,
A little over a week ago, I started my car to drive home. After reversing out of the car park, I noticed that as I took off my car slightly shuddered. I drove slowly to see if it did it again, but all seemed fine. Was handling speed and everything perfect. About ten minutes later, I came around a corner and as I was halfway up a hill, I lost all power in my car. I looked down to the dashboard and fairly certain I noticed the battery light flick on.

I put my car into park and hazards on to stop the car from rolling down into the intersection. I tried to restart the car a few times, but there was no luck. Just as I dialed my phone for help, I managed to restart my car. It seemed to drive just fine the whole way home. Once I was home, I turned the car off and restarted it - it started fine again. I havent driven the car for over a week, mainly because the thought of my car deciding to lose power while on a main road or highway slightly scares me. The battery was tested today, even though its four years old, it came back fine.

Do you think that it is the actual battery and can the car start again if it loses power like it did (that being a battery problem)? Or is it perhaps another problem altogether?

Thank you in advance,

Mara