7 files declare their use of SqlBase in Drupal 8

DrupalSqlBase.php in core/modules/migrate_drupal/src/Plugin/migrate/source/DrupalSqlBase.php

HighWaterTest.php in core/modules/migrate/tests/modules/migrate_high_water_test/src/Plugin/migrate/source/HighWaterTest.php

MigrationPluginListTest.php in core/modules/migrate/tests/src/Kernel/Plugin/MigrationPluginListTest.php

QueryBatchTest.php in core/modules/migrate/tests/modules/migrate_query_batch_test/src/Plugin/migrate/source/QueryBatchTest.php

SqlBaseTest.php in core/modules/migrate/tests/src/Unit/SqlBaseTest.php

Contains \Drupal\Tests\migrate\Unit\SqlBaseTest.

SqlBaseTest.php in core/modules/migrate/tests/src/Kernel/SqlBaseTest.php

Contains \Drupal\Tests\migrate\Kernel\SqlBaseTest.

TrackChangesTest.php in core/modules/migrate/tests/modules/migrate_track_changes_test/src/Plugin/migrate/source/TrackChangesTest.php