Calling entity.delete(flush: true) in a Spock test does not flush, nor does using withTransaction, one has to run both separately - grails

Question

I have a Grails 5.2.5 app with a Spock 2.0 test.
In it, I try to delete an entity like so:
def "experiment"() {
given:
MyEntity entity = new MyEntity().save(failOnError: true)).save(failOnError: true)
when:
entity.delete()
then:
MyEntity.count() == 0 // fails
}
It fails. The saved entity stays there after the deletion attempt. If I replace entity.delete() with any of the three options below, it still fails.
MyEntity.withSession {
entity.delete(flush: true, failOnError: true)
}
// OR
MyEntity.withTransaction {
entity.delete(flush: true, failOnError: true)
}
// OR
entity.delete(flush: true, failOnError: true)
Or if I remove failOnError:true.
I am basically currently unable to delete stuff from DB during a spock test and I used to be able to do that in Grails 2.x, so not sure how to migrate those tests.
Edit:
I had managed to delete an entity like so, but it makes no sense to me, why these should work and the aboves not:
def "experiment"() {
given:
MyEntity entity = new MyEntity().save(failOnError: true)
when:
entity.delete(flush: true) // here flush is necessary
MyEntity.withTransaction {
entity.delete()
}
then:
MyEntity.count() == 0 // passes
}
and to my utter amazement this works as well even without the flush, whereas above the flush is necessary:
def "experiment"() {
given:
MyEntity entity = new MyEntity().save(failOnError: true)
when:
MyEntity.withTransaction {
entity.delete()
}
entity.delete() // here flush is not necessary
then:
MyEntity.count() == 0 // passes
}
What sourcery is this..

Answer 1

Alright, the problem was I only flushed the delete, not the save operation. I thought I didn't have to since the saved entity was found during .count() operation.
Hibernate flushMode has COMMIT as default value instead of the AUTO from the past. Documentation has an error on this, I posted a PR to fix the doc, the change was mentioned only in release notes, but doc wasn't updated.
Since that has changed, now that I want to save entities and delete them in tests, I need to flush both operations.
So this works now okay:
def "experiment"() {
given:
MyEntity entity = new MyEntity().save(failOnError: true, flush: true) // flush was added here that wasn't here before
when:
entity.delete(flush: true) // flush needs to be here as well.
then:
MyEntity.count() == 0 // works now
}
Edit:
However, I'm still confused as to what's happening, because the test is running actually in flushMode AUTO, with SimpleMap GORM implementation, so it should have worked correctly without flushing. In Grails 2.5.6 with AUTO mode no flushes were necessary for it to work.
I had contacted grails-testing-support developers with a simple project demonstrating with unit tests, that the persistence behavior is not as I would expect, I hope they'll respond.
The issue: https://github.com/grails/grails-testing-support/issues/259
My repo demonstrating issue, you can run it locally with Grails 5.2.5