\Drupal\KernelTests\Core\Config\ConfigEntityValidationTestBase::testRequiredPropertyValuesMissing attempts to blindly set all required properties to NULL and assert a validation error.
But if the property being set is typed (i.e enforced at a language level) then setting it to NULL makes the test fail with a TypeError and no way to reuse the base class without overriding the whole method.
Create a config entity with a typed property e.g.
protected string $something
Attempt to add validation tests using \Drupal\KernelTests\Core\Config\ConfigEntityValidationTestBase
see testRequiredPropertyValuesMissing blow up with a TypeError
Catch TypeError and move on, validation is provided at the language level
Active
11.0 🔥
configuration system
Nice one @annmarysruthy - I think it in terms of adding a test, making one of the properties like weight on \Drupal\config_test\Entity\ConfigTest typed and adding a config validation test for that entity-type would demonstrate the issue.