/**
* {@inheritdoc}
*/
protected function prepareMigration(MigrationInterface $migration)
{
// File migrations need a source_base_path.
// @see MigrateUpgradeRunBatch::run
$destination = $migration->getDestinationConfiguration();
if ($destination['plugin'] === 'entity:file') {
// Make sure we have a single trailing slash.
$source = $migration->getSourceConfiguration();
$source['site_path'] = 'core/modules/simpletest';
$source['constants']['source_base_path'] = \Drupal::root() . '/';
$migration->set('source', $source);
}
}