The Travis contains a WP_MULTISITE=1 variable for both the matrix environment variables and the include environment variables.

While the other variables, WP_VERSION and PHPUNIT_VERSION, are used, I don't see that WP_MULTISITE is used anywhere.

Additionally, the test file does not include any multisite tests. I think that all unit test with WP_MULTISITE=1 are duplicates of their WP_MULTISITE=0 versions and should be removed as they increase Travis build times and unnecessarily use Travis resources.