From Nookipedia, the Animal Crossing wiki

Welcome to the Nookipedia Sandbox. This is where you can test out new templates or ideas before putting them onto pages. Please bear in mind that this page is cleaned every month so be sure to save your template somewhere else in case it gets archived by mistake.

Note that you can create subpages in your user page, so instead of writing your tests here, you could do it in Special:MyPage/Sandbox.