https://api.drupal.org/api/drupal/core%21modules%21migrate%21tests%21src%21Kernel%21MigrateEventsTest.php/9
MigrateEventsTest.php | Drupal API
phpdrupalapi
https://api.drupal.org/api/drupal/core%21modules%21migrate%21tests%21src%21Kernel%21MigrateEventsTest.php/property/MigrateEventsTest%3A%3Astate/8.9.x
MigrateEventsTest::$state | Drupal API
statedrupalapi