good first issuehelp wanted
Description
As of this writing, the core impress.js API has ok test coverage, as does the navigation plugin. All other plugins were essentially implemented without tests. (Sorry, historical reasons.)
Now that they're merged to upstream impress.js though, we do have a goal of adding test coverage for all of them. Basically, it would be nice to have at least one src/plugins/pluginname/pluginname_tests.js file for each plugin.
This is a catch all ticket. If you want to help in creating tests for a plugin, please file a new issue with a title like "Add tests for plugin pluginname"
Related: #657