WordPress has Theme Unit Test data that contains all the different type of post/page data as long as quite a number of posts (39 published posts, and in total, has installed 41 posts) and pages (something like 10 or 15). There is a Monster Widget plugin that will allow you to place one widget that contains all the widgets that are available from WordPress (archives, categories, pages, etc). There is also another plugin that will help in development to sync the sites: WP Migrate DB Pro and is covered in the “WordPress Plugins, Moving WordPress with WP Migrate DB” course.