Why is one phpunit test throwing an error on one class when all other classes are similar without error?

I’m working on the Liquid Messages plugin. There are some basic PHPUnit tests existing for it and when I run phpunit all pass except for one. It errors out: There was 1 error: 1) GCS_Async_Test::test_class_access Exception: Invalid GC_Sermons_Plugin property: async /long/path/wp-content/plugins/lqd-messages/gc-sermons.php:330 /long/path/wp-content/plugins/lqd-messages/tests/test-async.php:10 The weird thing is that gc-sermons.php contains a number of properties similar to…