reverted:
--- b/core/modules/comment/src/Tests/d6/MigrateCommentTest.php
+++ a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentTest.php
@@ -2,18 +2,17 @@
 
 /**
  * @file
+ * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentTest.
- * Contains \Drupal\comment\Tests\d6\MigrateCommentTest.
  */
 
+namespace Drupal\migrate_drupal\Tests\d6;
-namespace Drupal\comment\Tests\d6;
 
 use Drupal\comment\Tests\CommentTestTrait;
-use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Upgrade comments.
  *
+ * @group migrate_drupal
- * @group comment
  */
 class MigrateCommentTest extends MigrateDrupal6TestBase {
 
reverted:
--- b/core/modules/comment/src/Tests/d6/MigrateCommentTypeTest.php
+++ a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentTypeTest.php
@@ -2,18 +2,17 @@
 
 /**
  * @file
+ * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentTypeTest.
- * Contains \Drupal\comment\Tests\d6\MigrateCommentTypeTest.
  */
 
+namespace Drupal\migrate_drupal\Tests\d6;
-namespace Drupal\comment\Tests\d6;
 
 use Drupal\comment\Entity\CommentType;
-use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Upgrade comment type.
  *
+ * @group migrate_drupal
- * @group comment
  */
 class MigrateCommentTypeTest extends MigrateDrupal6TestBase {
 
reverted:
--- b/core/modules/comment/src/Tests/d6/MigrateCommentVariableDisplayBase.php
+++ a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentVariableDisplayBase.php
@@ -2,12 +2,10 @@
 
 /**
  * @file
+ * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentVariableDisplayBase.
- * Contains \Drupal\comment\Tests\d6\MigrateCommentVariableDisplayBase.
  */
 
+namespace Drupal\migrate_drupal\Tests\d6;
-namespace Drupal\comment\Tests\d6;
-
-use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Base class for Drupal 6 comment variables to Drupal 8 entity display tests.
reverted:
--- b/core/modules/comment/src/Tests/d6/MigrateCommentVariableEntityDisplayTest.php
+++ a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentVariableEntityDisplayTest.php
@@ -2,15 +2,15 @@
 
 /**
  * @file
+ * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentVariableEntityDisplayTest.
- * Contains \Drupal\comment\Tests\d6\MigrateCommentVariableEntityDisplayTest.
  */
 
+namespace Drupal\migrate_drupal\Tests\d6;
-namespace Drupal\comment\Tests\d6;
 
 /**
  * Upgrade comment variables to entity.display.node.*.default.yml.
  *
+ * @group migrate_drupal
- * @group comment
  */
 class MigrateCommentVariableEntityDisplayTest extends MigrateCommentVariableDisplayBase {
 
reverted:
--- b/core/modules/comment/src/Tests/d6/MigrateCommentVariableEntityFormDisplaySubjectTest.php
+++ a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentVariableEntityFormDisplaySubjectTest.php
@@ -2,17 +2,15 @@
 
 /**
  * @file
+ * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentVariableEntityFormDisplaySubjectTest.
- * Contains \Drupal\comment\Tests\d6\MigrateCommentVariableEntityFormDisplaySubjectTest.
  */
 
+namespace Drupal\migrate_drupal\Tests\d6;
-namespace Drupal\comment\Tests\d6;
-
-use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Upgrade comment subject variable to core.entity_form_display.comment.*.default.yml
  *
+ * @group migrate_drupal
- * @group comment
  */
 class MigrateCommentVariableEntityFormDisplaySubjectTest extends MigrateDrupal6TestBase {
 
reverted:
--- b/core/modules/comment/src/Tests/d6/MigrateCommentVariableEntityFormDisplayTest.php
+++ a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentVariableEntityFormDisplayTest.php
@@ -2,15 +2,15 @@
 
 /**
  * @file
+ * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentVariableEntityFormDisplayTest.
- * Contains \Drupal\comment\Tests\d6\MigrateCommentVariableEntityFormDisplayTest.
  */
 
+namespace Drupal\migrate_drupal\Tests\d6;
-namespace Drupal\comment\Tests\d6;
 
 /**
  * Upgrade comment variables to core.entity_form_display.node.*.default.yml.
  *
+ * @group migrate_drupal
- * @group comment
  */
 class MigrateCommentVariableEntityFormDisplayTest extends MigrateCommentVariableDisplayBase {
 
reverted:
--- b/core/modules/comment/src/Tests/d6/MigrateCommentVariableFieldTest.php
+++ a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentVariableFieldTest.php
@@ -2,18 +2,17 @@
 
 /**
  * @file
+ * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentVariableFieldTest.
- * Contains \Drupal\comment\Tests\d6\MigrateCommentVariableFieldTest.
  */
 
+namespace Drupal\migrate_drupal\Tests\d6;
-namespace Drupal\comment\Tests\d6;
 
 use Drupal\field\Entity\FieldStorageConfig;
-use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Upgrade comment variables to field.storage.node.comment.yml.
  *
+ * @group migrate_drupal
- * @group comment
  */
 class MigrateCommentVariableFieldTest extends MigrateDrupal6TestBase {
 
reverted:
--- b/core/modules/comment/src/Tests/d6/MigrateCommentVariableInstanceTest.php
+++ a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentVariableInstanceTest.php
@@ -2,17 +2,15 @@
 
 /**
  * @file
+ * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentVariableInstanceTest.
- * Contains \Drupal\comment\Tests\d6\MigrateCommentVariableInstanceTest.
  */
 
+namespace Drupal\migrate_drupal\Tests\d6;
-namespace Drupal\comment\Tests\d6;
-
-use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Upgrade comment variables to field.instance.node.*.comment.yml.
  *
+ * @group migrate_drupal
- * @group comment
  */
 class MigrateCommentVariableInstanceTest extends MigrateDrupal6TestBase {
 
only in patch2:
unchanged:
--- a/core/modules/comment/config/schema/comment.schema.yml
+++ b/core/modules/comment/config/schema/comment.schema.yml
@@ -102,3 +102,39 @@ field.field_settings.comment:
     preview:
       type: integer
       label: 'Preview comment'
+
+migrate.source.d6_comment:
+  type: migrate_source_sql
+  label: 'Drupal 6 comment'
+  mapping:
+    constants:
+      type: mapping
+      label: 'Constants'
+      mapping:
+        entity_type:
+          type: string
+          label: 'Entity type'
+
+migrate.source.d6_comment_variable_per_comment_type:
+  type: migrate_source_sql
+  label: 'Drupal 6 comment variable'
+  mapping:
+    constants:
+      type: migrate_entity_constant
+      label: 'Constants'
+
+migrate.source.d6_comment_entity_form_display_subject:
+  type: migrate_source_sql
+  label: 'Drupal 6 comment subject entity form display'
+  mapping:
+    constants:
+      type: migrate_entity_constant
+      label: 'Constants'
+
+migrate.source.d6_comment_variable:
+  type: migrate_source_sql
+  label: 'Drupal 6 comment variable'
+  mapping:
+    constants:
+      type: migrate_entity_constant
+      label: 'Constants'
only in patch2:
unchanged:
--- a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentTest.php
+++ b/core/modules/comment/src/Tests/Migrate/d6/MigrateCommentTest.php
@@ -2,17 +2,18 @@
 
 /**
  * @file
- * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentTest.
+ * Contains \Drupal\comment\Tests\Migrate\d6\MigrateCommentTest.
  */
 
-namespace Drupal\migrate_drupal\Tests\d6;
+namespace Drupal\comment\Tests\Migrate\d6;
 
 use Drupal\comment\Tests\CommentTestTrait;
+use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Upgrade comments.
  *
- * @group migrate_drupal
+ * @group comment
  */
 class MigrateCommentTest extends MigrateDrupal6TestBase {
 
only in patch2:
unchanged:
--- a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentTypeTest.php
+++ b/core/modules/comment/src/Tests/Migrate/d6/MigrateCommentTypeTest.php
@@ -2,17 +2,18 @@
 
 /**
  * @file
- * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentTypeTest.
+ * Contains \Drupal\comment\Tests\Migrate\d6\MigrateCommentTypeTest.
  */
 
-namespace Drupal\migrate_drupal\Tests\d6;
+namespace Drupal\comment\Tests\Migrate\d6;
 
 use Drupal\comment\Entity\CommentType;
+use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Upgrade comment type.
  *
- * @group migrate_drupal
+ * @group comment
  */
 class MigrateCommentTypeTest extends MigrateDrupal6TestBase {
 
only in patch2:
unchanged:
--- a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentVariableDisplayBase.php
+++ b/core/modules/comment/src/Tests/Migrate/d6/MigrateCommentVariableDisplayBase.php
@@ -2,10 +2,12 @@
 
 /**
  * @file
- * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentVariableDisplayBase.
+ * Contains \Drupal\comment\Tests\Migrate\d6\MigrateCommentVariableDisplayBase.
  */
 
-namespace Drupal\migrate_drupal\Tests\d6;
+namespace Drupal\comment\Tests\Migrate\d6;
+
+use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Base class for Drupal 6 comment variables to Drupal 8 entity display tests.
only in patch2:
unchanged:
--- a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentVariableEntityDisplayTest.php
+++ b/core/modules/comment/src/Tests/Migrate/d6/MigrateCommentVariableEntityDisplayTest.php
@@ -2,15 +2,15 @@
 
 /**
  * @file
- * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentVariableEntityDisplayTest.
+ * Contains \Drupal\comment\Tests\Migrate\d6\MigrateCommentVariableEntityDisplayTest.
  */
 
-namespace Drupal\migrate_drupal\Tests\d6;
+namespace Drupal\comment\Tests\Migrate\d6;
 
 /**
  * Upgrade comment variables to entity.display.node.*.default.yml.
  *
- * @group migrate_drupal
+ * @group comment
  */
 class MigrateCommentVariableEntityDisplayTest extends MigrateCommentVariableDisplayBase {
 
only in patch2:
unchanged:
--- a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentVariableEntityFormDisplaySubjectTest.php
+++ b/core/modules/comment/src/Tests/Migrate/d6/MigrateCommentVariableEntityFormDisplaySubjectTest.php
@@ -2,15 +2,17 @@
 
 /**
  * @file
- * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentVariableEntityFormDisplaySubjectTest.
+ * Contains \Drupal\comment\Tests\Migrate\d6\MigrateCommentVariableEntityFormDisplaySubjectTest.
  */
 
-namespace Drupal\migrate_drupal\Tests\d6;
+namespace Drupal\comment\Tests\Migrate\d6;
+
+use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Upgrade comment subject variable to core.entity_form_display.comment.*.default.yml
  *
- * @group migrate_drupal
+ * @group comment
  */
 class MigrateCommentVariableEntityFormDisplaySubjectTest extends MigrateDrupal6TestBase {
 
only in patch2:
unchanged:
--- a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentVariableEntityFormDisplayTest.php
+++ b/core/modules/comment/src/Tests/Migrate/d6/MigrateCommentVariableEntityFormDisplayTest.php
@@ -2,15 +2,15 @@
 
 /**
  * @file
- * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentVariableEntityFormDisplayTest.
+ * Contains \Drupal\comment\Tests\Migrate\d6\MigrateCommentVariableEntityFormDisplayTest.
  */
 
-namespace Drupal\migrate_drupal\Tests\d6;
+namespace Drupal\comment\Tests\Migrate\d6;
 
 /**
  * Upgrade comment variables to core.entity_form_display.node.*.default.yml.
  *
- * @group migrate_drupal
+ * @group comment
  */
 class MigrateCommentVariableEntityFormDisplayTest extends MigrateCommentVariableDisplayBase {
 
only in patch2:
unchanged:
--- a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentVariableFieldTest.php
+++ b/core/modules/comment/src/Tests/Migrate/d6/MigrateCommentVariableFieldTest.php
@@ -2,17 +2,18 @@
 
 /**
  * @file
- * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentVariableFieldTest.
+ * Contains \Drupal\comment\Tests\Migrate\d6\MigrateCommentVariableFieldTest.
  */
 
-namespace Drupal\migrate_drupal\Tests\d6;
+namespace Drupal\comment\Tests\Migrate\d6;
 
 use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Upgrade comment variables to field.storage.node.comment.yml.
  *
- * @group migrate_drupal
+ * @group comment
  */
 class MigrateCommentVariableFieldTest extends MigrateDrupal6TestBase {
 
only in patch2:
unchanged:
--- a/core/modules/migrate_drupal/src/Tests/d6/MigrateCommentVariableInstanceTest.php
+++ b/core/modules/comment/src/Tests/Migrate/d6/MigrateCommentVariableInstanceTest.php
@@ -2,15 +2,17 @@
 
 /**
  * @file
- * Contains \Drupal\migrate_drupal\Tests\d6\MigrateCommentVariableInstanceTest.
+ * Contains \Drupal\comment\Tests\Migrate\d6\MigrateCommentVariableInstanceTest.
  */
 
-namespace Drupal\migrate_drupal\Tests\d6;
+namespace Drupal\comment\Tests\Migrate\d6;
+
+use Drupal\migrate_drupal\Tests\d6\MigrateDrupal6TestBase;
 
 /**
  * Upgrade comment variables to field.instance.node.*.comment.yml.
  *
- * @group migrate_drupal
+ * @group comment
  */
 class MigrateCommentVariableInstanceTest 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
@@ -39,34 +39,6 @@ migrate.source.variable:
           type: string
           label: 'Slash'
 
-migrate.source.d6_comment:
-  type: migrate_source_sql
-  label: 'Drupal 6 comment'
-  mapping:
-    constants:
-      type: mapping
-      label: 'Constants'
-      mapping:
-        entity_type:
-          type: string
-          label: 'Entity type'
-
-migrate.source.d6_comment_variable_per_comment_type:
-  type: migrate_source_sql
-  label: 'Drupal 6 comment variable'
-  mapping:
-    constants:
-      type: migrate_entity_constant
-      label: 'Constants'
-
-migrate.source.d6_comment_entity_form_display_subject:
-  type: migrate_source_sql
-  label: 'Drupal 6 comment subject entity form display'
-  mapping:
-    constants:
-      type: migrate_entity_constant
-      label: 'Constants'
-
 migrate.source.d6_menu_link:
   type: migrate_source_sql
   label: 'Drupal 6 menu link'
@@ -138,14 +110,6 @@ migrate.source.variable_multirow:
         type: string
         label: 'Variable'
 
-migrate.source.d6_comment_variable:
-  type: migrate_source_sql
-  label: 'Drupal 6 comment variable'
-  mapping:
-    constants:
-      type: migrate_entity_constant
-      label: 'Constants'
-
 migrate.source.d6_contact_settings:
   type: migrate_source_sql
   label: 'Drupal 6 contact settings'