background_validation.js is failing on ephemeralForTest because it expects a collection MODE_IX lock to be possible and tries to run CRUD concurrently with background validation. I haven't figured out how to stop it running there, yet, because the test already has requires_wiredtiger.

requires_persistence:
background_validation.js cannot run on inMemory, even though it is WT, because inMemory doesn't have checkpoints on which to run background validation.