diff --git b/core/modules/migrate/src/Tests/MigrateTestBase.php a/core/modules/migrate/src/Tests/MigrateTestBase.php
index 7b2dd98..4138ede 100644
--- b/core/modules/migrate/src/Tests/MigrateTestBase.php
+++ a/core/modules/migrate/src/Tests/MigrateTestBase.php
@@ -65,10 +65,9 @@ protected function setUp() {
   /**
    * Changes the database connection to the prefixed one.
    *
-   * @todo this can be removed when we don't rely on global connections. https://www.drupal.org/node/2552791
+   * @todo Remove when we don't use global. https://www.drupal.org/node/2552791
    */
   private function createMigrationConnection() {
-
     // If the backup already exists, something went terribly wrong.
     // This case is possible, because database connection info is a static
     // global state construct on the Database class, which at least persists
@@ -109,6 +108,8 @@ protected function tearDown() {
 
   /**
    * Cleans up the test migrate connection.
+   *
+   * @todo Remove when we don't use global. https://www.drupal.org/node/2552791
    */
   private function cleanupMigrateConnection() {
     Database::removeConnection('migrate');