“Test” doesn’t seem big enough to think about the way you have to engage in the viva.
A test feels like a little thing, a one-time intervention where you are measured, checked and analysed. That’s not the viva. Maybe we could consider the viva being like a car’s MOT: a check that you are researcher-ready. You have everything in place and are ready to run as a researcher, if you wanted to, but still that wouldn’t feel quite right.
Better to say you’re examined in the viva. You’re challenged by the viva. You defend your work in the viva.
But it’s not enough to say that you’re simply tested by it. The viva is not so great and big as to be the most important thing you will ever do, but it’s not so small as to be simply a test.