Generated unittests break with phpunit 9 (required by the v10 testingframework)

[cypelt]

Describe the bug
Testing attributes has been removed from phpunit sebastianbergmann/phpunit#3339 (comment)
calls like self::assertAttributeEquals break
To Reproduce
run the unit tests of setters generated by the extension builder
Expected behavior
do not generate broken unit tests.

TYPO3 Version
v10, phpunit 9
Extension Builder Version:
v10.0.1

Additional context
as stated in the thread, this is considered bad practice (protected/private attributes). So to test if the attribute has been set we need to check it via the "public api" which would be the getter.