ScalaTestPlay-Plus running code before a test, but after the app has been created

In ScalaTest (+ play) you can use the BeforeAndAfter trait to run code before or after a test.
However, you cannot access the app (created using GuiceApplicationBuilder) when using GuiceOneServerPerTest.

Test isn't running yet so application is not available

How do you run some code before the tests start, but after the application is available?