TYPO3 Core

when setting up a project composer based with

composer create-project typo3/cms cms ^8.7 -n

the command failes with

...
Generating autoload files

  [RuntimeException]
  Could not scan for classes inside "typo3/sysext/extbase/Tests/Unit/Object/Container/Fixtures/" which does not appear to
  be a file nor a folder

This happens for the classmap entry in sysext:extbase/composer.jons line 41, that tries to load Test classes into autoload-dev autoloading. But thanks to Testclasses being excluded from the operation (git attributes I guess) the folder does not exist and the command fails.

One can work around that by adding --prefer-source to the create-project command, but that slows down the whole process a lot and ends up with all test classes in place.