A WordPress plugin that makes it easy to add a Network-wide "Site Directory" to your WP Multisite install.
Multisite Directory is intended only for WP Multisite installs (as the name implies). Therefore, when you run tests locally, do:
WP_MULTISITE=1 phpunit
If you don't set the WP_MULTISITE
environment variable, the tests will still run, but you will be testing a single-site install, and the plugin doesn't really do anything interesting on single-site installs (for obvious reasons).