I very much agree--all gear should be tested in the back yard (or on a car-camping trip if you don't have a back yard). This is especially important for beginners, to learn not only how to use their gear but to practice equally important outdoor skills (such as body temperature regulation, keeping dry, water treatment, fire building [where legal], cooking, etc.).

Sometimes this is hard to do if you live in a mild climate where it doesn't freeze very much, like the coastal regions of the far west. Winter tests where I live involve mostly wind and rain rather than snow or below-freezing temperatures, although even these are valid tests. But at least in the back yard you can practice with the new tent (so you can pitch it in high wind, pouring rain, in the dark, without the directions), try out the new sleeping pad, practice setting up and breaking down camp so you can do it faster (my perpetual problem), practice cooking in inclement weather.

The next step after back-yard camping is car-camping. Of course if you're an apartment dweller with no back yard, car-camping is what you start with! If you live in a mild climate, car-camping in colder areas (mountains?) is the only way you can learn to cope with cold weather. With the car close by, if you mess up, you can retreat to your car and turn on the heater, or just pack up and go home.

Just remember to do this testing during bad weather, not just on warm sunny days and clear nights. No matter how closely you watch weather forecasts (which aren't always that reliable!), you need to be able to cope with the inevitable nasty stuff--again, doing your learning in a place where you can safely bail out!

I've found that the shower is a great place to test rain gear. If there are any leaks, you'll know in 20 minutes! It's also a good idea to use a hose (again for 20 minutes) after you've seam-sealed your shelter. It's much easier to find and fix that 1/4 inch space you skipped while at home instead of in a Rocky Mountain cloudburst 15 miles from the trailhead, when the skipped spot turns out to be directly over your sleeping bag!

No matter how expert you are, be sure to test out all new gear before you've left the trailhead, preferably under conditions in which you can keep it new and clean and therefore returnable. The money/comfort/even life you save may be your own!