TP Importer helps theme users to easily use dummy data with a few available options, including Theme Unit test, WooCommerce Dummy Data, Widget Monster.
After choosing the topic that you want, just click Import. When the progress bar will be done, it means all data are ready.
Besides, the plugin also provides a manual import by uploading from computer with some popular extensions (XML, JSON, WIE, DAT).
For theme developers, if you want to provide more dummy data options to your users, you can use some available hooks in the plugin. Dummy data files can come from anywhere on the Internet, of course you can push those files to your theme or plugin.
TP Toolkit provides for theme developers basic fields like Taxonomy, Metabox, Customizer, Menu Meta, Widget Fields, as well as other advanced fields.