reverted:
--- b/core/modules/block_content/src/Tests/d6/MigrateBlockContentTest.php
+++ a/core/modules/migrate_drupal/src/Tests/d6/MigrateBlockContentTest.php
@@ -2,18 +2,17 @@
 
 /**
  * @file
+ * Contains \Drupal\migrate_drupal\Tests\d6\MigrateBlockContentTest.
- * Contains \Drupal\block_content\Tests\d6\MigrateBlockContentTest.
  */
 
+namespace Drupal\migrate_drupal\Tests\d6;
-namespace Drupal\block_content\Tests\d6;
 
 use Drupal\block_content\Entity\BlockContent;
-use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Upgrade custom blocks.
  *
+ * @group migrate_drupal
- * @group block_content
  */
 class MigrateBlockContentTest extends MigrateDrupal6TestBase {
 
only in patch2:
unchanged:
--- a/core/modules/block_content/config/schema/block_content.schema.yml
+++ b/core/modules/block_content/config/schema/block_content.schema.yml
@@ -16,3 +16,15 @@ block_content.type.*:
     description:
       type: text
       label: 'Description'
+
+migrate.source.d6_box:
+  type: migrate_source_sql
+  label: 'Drupal 6 box'
+  mapping:
+    constants:
+      type: mapping
+      label: 'Constants'
+      mapping:
+        type:
+          type: string
+          label: 'Type'
only in patch2:
unchanged:
--- a/core/modules/migrate_drupal/src/Tests/d6/MigrateBlockContentTest.php
+++ b/core/modules/block_content/src/Tests/Migrate/d6/MigrateBlockContentTest.php
@@ -2,17 +2,18 @@
 
 /**
  * @file
- * Contains \Drupal\migrate_drupal\Tests\d6\MigrateBlockContentTest.
+ * Contains \Drupal\block_content\Tests\Migrate\d6\MigrateBlockContentTest.
  */
 
-namespace Drupal\migrate_drupal\Tests\d6;
+namespace Drupal\block_content\Tests\Migrate\d6;
 
 use Drupal\block_content\Entity\BlockContent;
+use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Upgrade custom blocks.
  *
- * @group migrate_drupal
+ * @group block_content
  */
 class MigrateBlockContentTest extends MigrateDrupal6TestBase {
 
only in patch2:
unchanged:
--- a/core/modules/migrate_drupal/config/schema/migrate_drupal.source.schema.yml
+++ b/core/modules/migrate_drupal/config/schema/migrate_drupal.source.schema.yml
@@ -75,18 +75,6 @@ migrate.source.d6_menu_link:
       type: migrate_entity_constant
       label: 'Constants'
 
-migrate.source.d6_box:
-  type: migrate_source_sql
-  label: 'Drupal 6 box'
-  mapping:
-    constants:
-      type: mapping
-      label: 'Constants'
-      mapping:
-        type:
-          type: string
-          label: 'Type'
-
 migrate.source.d6_taxonomy_vocabulary:
   type: migrate_source_sql
   label: 'Drupal 6 field instance form display'