Btw, in order to understand the tests, I actually broke it up into multiple tests. IMO testSynchAsConfigured were really 4 different tests rolled into one test method -
https://github.com/hferentschik/hibernate-search/commit/e8c3f4e8e67fc4cdb91ca64371478ea6773018d4

Still the same problem though, the refactored test passes with Alpha1 and fails with Beta1.