Test at eye level on an interior wall, where moisture is less likely to be a factor. Ligeri cuts a V-shaped flap with a razor blade and then tries to pull the paper away. Take a spray bottle and wet it to make sure the glue that was used was a regular wallcovering adhesive and not an adhesive doctored with a prep coat. People don't often test the adhesive, but that's a very important thing to test. If you're estimating removal in a master bedroom, test behind the headboard.
Kitchens are difficult to test because they get remodeled more often than any other room.
In a bathroom, always test a wall, never a ceiling. The customer will likely ask that you test the ceiling if the paper's already loose near the shower. But there's probably more paper on the wall than the ceiling. In a dining room with a chair rail, check above the rail, where the bulk of the redecorating will have taken place. Ligeri also advised that contractors check the porosity of the wallcovering to be removed.