Symfony version(s) affected: 4.4

Somehow our testsuite became extremely slow after updating to 4.4. It's a regular API platform setup, using hautelook fixtures. So DB is reloaded on every test.

In the var/cache/test it seems to boot/cache a compiled container container per testcase. If i abort after first testcase, and then restart the testsuite it seems to pick up the existing container.

Moreover, the behavior is exposed using:

# FAST
rm -rf var/cache/test
bin/phpunit

# SLOW
rm -rf var/cache/test
bin/console c:c -e test
bin/phpunit

# ALSO SLOW
rm -rf var/cache/test
bin/console c:c --no-warmup -e test
bin/phpunit

Im not sure where to look for now, hints welcome :) i've updated all recipes etc. so everything is "latest 4.4".