Looks like this is causing the test error on the [Travis CI build](https://travis-ci.org/groovecoder/wp-promote-mdn/jobs/17242863).

The fix is probably to add an $old_instance argument to [WidgetTest.php:16](https://github.com/trishasalas/wp-promote-mdn/blob/923fcfb68d623e8b3a4cd2f2a9ffdc8680e5105d/tests/WidgetTest.php#L16)