I understand what you are feeling. About 1 month ago I had my first test. When I was first asked to test I felt equally as unsure as you are describing. To overcome this I spent a couple of weeks focusing on the testing techniques and not too much else. I over prepared myself to such an extent that by the time it came around I found myself surprisingly not nervous. To think back to it now the test was a blur and I feel like I must have had my eyes closed but it went very well.
Get those technique names down and visualize yourself performing each one slowly and smoothly, and get ready to surprise yourself.