"Once you’ve made a design, it gets harder to change, so it’s best to test early and test often. As each test only takes a few minutes to set up and run, it’s something you can easily build into your timeline to complete projects on time. Remember the old saying from Frank Lloyd Wright, 'You can use an eraser on the drafting table or a sledgehammer on the construction site'"
It's a good article. You should go read the rest.