The failure as it actually appeared in a full 'mvn -B test' run of this repository,
before hibernate.cache.use_second_level_cache was pinned to false in application.yml.
It is order-dependent: running the two classes on their own passes.

[ERROR]   ImmutableEntityTest.nativeSqlUpdate_onImmutableEntity_alwaysWorks:184 » Rollback Error while committing the transaction [Unable to perform afterTransactionCompletion callback: Cache[com.ank

[ERROR] Tests run: 140, Failures: 0, Errors: 1, Skipped: 0

Why every Spring context in the project had a second-level cache at all:
$ mvn -o -B test -Dtest=JCacheOnClasspathAutoEnablesL2Test
second-level cache enabled = true
region factory            = org.hibernate.cache.jcache.internal.JCacheRegionFactory
explicitly configured?    = true

Nothing in src/main/resources/application.yml mentions caching:
$ grep -ic cache src/main/resources/application.yml
0