resetting unit completion percents

I have created a course and it consists of 5 units. There are 2 pages to each unit. After setting those up I click on preview button and test out the questions, just to try and figure out the lay of how things appear after completing a unit so you can see how you progress to a new unit. But I have tested so many times it is like the course is complete. Is that course done and I have to make a duplicate to start all over?
Stuck and confused.
Sis