JUnit 5.1 allows you to [register an extension programmatically](https://junit.org/junit5/docs/current/user-guide/#extensions-registration-programmatic) by adding a field to your class as shown below. Similiar to JUnit4s Rule/ClassRule. ``` @RegisterExtension JerseyExtension jerseyExtension = new JerseyExtension(this::configureJersey); ``` (apologies I haven't yet had a chance to add a failing test for this)