Consider the unset of _core in \Drupal\FunctionalTests\Core\Recipe\StandardRecipeTest::testStandard()

Problem/Motivation

In \Drupal\FunctionalTests\Core\Recipe\StandardRecipeTest::testStandard() we unset _core to make recipes work. We should think about the implications of this some more.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes