PHPUnit 10 marks empty data provider as invalid with the text "Empty data set provided by data provider" and count this as errors.
Some of the provider of the abstract AbstractSchemaTestBase are designed to return empty array in case there is no abstract schema change folder.
Throwing an exception (like markTestSkipped) does not work under PHPUnit 10.
Example from FlaggedRevs:
1) MediaWiki\Extension\FlaggedRevs\Tests\Structure\FlaggedRevsSchemaTest::testSchemaChangesAreValid The data provider specified for MediaWiki\Extension\FlaggedRevs\Tests\Structure\FlaggedRevsSchemaTest::testSchemaChangesAreValid is invalid Empty data set provided by data provider FlaggedRevs\tests\phpunit\structure\FlaggedRevsSchemaTest.php:49 2) MediaWiki\Extension\FlaggedRevs\Tests\Structure\FlaggedRevsSchemaTest::testSchemaChangesHaveAutoGeneratedFiles The data provider specified for MediaWiki\Extension\FlaggedRevs\Tests\Structure\FlaggedRevsSchemaTest::testSchemaChangesHaveAutoGeneratedFiles is invalid Empty data set provided by data provider FlaggedRevs\tests\phpunit\structure\FlaggedRevsSchemaTest.php:89