By catch on
Change record status: 
Draft (View all draft change records)
Project: 
Drupal core
Introduced in branch: 
12.0.x
Introduced in version: 
12.0.0
Issue links: 
https://www.drupal.org/node/3067979
Description: 

As of Drupal 12.0.0, Drupal core release packages will no longer include tests.

Custom CI pipelines that want to run tests against a tagged release of Drupal core should install with composer --prefer-source first.

When applying patches against Drupal core with composer, changes to test files should be removed from the patch file so that it continues to apply.

Impacts: 
Site builders, administrators, editors
Module developers