diff -u b/core/modules/migrate/src/Audit/IdAuditor.php b/core/modules/migrate/src/Audit/IdAuditor.php
--- b/core/modules/migrate/src/Audit/IdAuditor.php
+++ b/core/modules/migrate/src/Audit/IdAuditor.php
@@ -32,7 +32,7 @@
       throw new AuditException($migration, "ID map does not implement $interface");
     }
 
-    if ($destination->max() > $id_map->max()) {
+    if ($destination->getHighestId() > $id_map->getHighestId()) {
       return static::conflict($migration);
     }
     return [];
@@ -67,15 +67,8 @@
     $conflict = [
       $base_id => $base_id,
     ];
+    $conflict[$base_id] = (string) $migration->label();
 
-    $label = $migration->label();
-    if (is_string($label)) {
-      $conflict[$base_id] = $label;
-    }
-    elseif ($label instanceof TranslatableMarkup) {
-      $arguments = $label->getArguments();
-      $conflict[$base_id] = isset($arguments['@label']) ? $arguments['@label'] : $label->render();
-    }
     return $conflict;
   }
 
diff -u b/core/modules/migrate/src/Audit/MaximumValueInterface.php b/core/modules/migrate/src/Audit/MaximumValueInterface.php
--- b/core/modules/migrate/src/Audit/MaximumValueInterface.php
+++ b/core/modules/migrate/src/Audit/MaximumValueInterface.php
@@ -5,13 +5,13 @@
 /**
  * Defines an interface for destination and ID maps which track a highest ID.
  *
- * When implemented by destination plugins, max() should return the highest ID
- * of the destination entity type that exists in the system. So, for example,
- * the entity:node plugin should return the highest node ID that exists,
- * regardless of whether it was created by a migration.
+ * When implemented by destination plugins, getHighestId() should return the
+ * highest ID of the destination entity type that exists in the system. So, for
+ * example, the entity:node plugin should return the highest node ID that
+ * exists, regardless of whether it was created by a migration.
  *
- * When implemented by an ID map, max() should return the highest migrated ID
- * of the destination entity type.
+ * When implemented by an ID map, getHighestId() should return the highest
+ * migrated ID of the destination entity type.
  */
 interface MaximumValueInterface {
 
@@ -22,5 +22,5 @@
    *   The highest ID.
    */
-  public function max();
+  public function getHighestId();
 
 }
diff -u b/core/modules/migrate/src/Plugin/Migration.php b/core/modules/migrate/src/Plugin/Migration.php
--- b/core/modules/migrate/src/Plugin/Migration.php
+++ b/core/modules/migrate/src/Plugin/Migration.php
@@ -20,9 +20,8 @@
  * Configuration options:
  *
  *   - audit: If set to TRUE, the migration's IDs will be audited. This means
- *     that, for the entity type this migration creates, if the highest
- *     destination ID is greater than the highest source ID, a warning will be
- *     displayed that entities might be overwritten.
+ *     that if the highest destination ID is greater than the highest source ID,
+ *     a warning will be displayed that entities might be overwritten.
  */
 class Migration extends PluginBase implements MigrationInterface, RequirementsInterface, ContainerFactoryPluginInterface {
 
diff -u b/core/modules/migrate/src/Plugin/migrate/destination/EntityContentBase.php b/core/modules/migrate/src/Plugin/migrate/destination/EntityContentBase.php
--- b/core/modules/migrate/src/Plugin/migrate/destination/EntityContentBase.php
+++ b/core/modules/migrate/src/Plugin/migrate/destination/EntityContentBase.php
@@ -295,7 +295,7 @@
   /**
    * {@inheritdoc}
    */
-  public function max() {
+  public function getHighestId() {
     $query = $this->storage->getQuery()
       ->sort($this->getKey('id'), 'DESC')
       ->range(0, 1);
diff -u b/core/modules/migrate/src/Plugin/migrate/destination/EntityRevision.php b/core/modules/migrate/src/Plugin/migrate/destination/EntityRevision.php
--- b/core/modules/migrate/src/Plugin/migrate/destination/EntityRevision.php
+++ b/core/modules/migrate/src/Plugin/migrate/destination/EntityRevision.php
@@ -81,7 +81,7 @@
   /**
    * {@inheritdoc}
    */
-  public function max() {
+  public function getHighestId() {
     $query = $this->storage->getQuery()
       ->sort($this->getKey('revision'), 'DESC')
       ->range(0, 1);
diff -u b/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php b/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
--- b/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
+++ b/core/modules/migrate/src/Plugin/migrate/id_map/Sql.php
@@ -13,6 +13,7 @@
 use Drupal\migrate\MigrateException;
 use Drupal\migrate\MigrateMessageInterface;
 use Drupal\migrate\Plugin\MigrateIdMapInterface;
+use Drupal\migrate\Plugin\MigrationPluginManagerInterface;
 use Drupal\migrate\Row;
 use Drupal\migrate\Event\MigrateEvents;
 use Drupal\migrate\Event\MigrateMapSaveEvent;
@@ -85,6 +86,13 @@
   protected $migration;
 
   /**
+   * The migration plugin manager.
+   *
+   * @var \Drupal\migrate\Plugin\MigrationPluginManagerInterface
+   */
+  protected $migration_plugin_manager;
+
+  /**
    * The source ID fields.
    *
    * @var array
@@ -155,12 +163,15 @@
    *   The migration to do.
    * @param \Symfony\Component\EventDispatcher\EventDispatcherInterface $event_dispatcher
    *   The event dispatcher.
+   * @param \Drupal\migrate\Plugin\MigrationPluginManagerInterface $migration_plugin_manager
+   *   The migration plugin manager.
    */
-  public function __construct(array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration, EventDispatcherInterface $event_dispatcher) {
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration, EventDispatcherInterface $event_dispatcher, MigrationPluginManagerInterface $migration_plugin_manager) {
     parent::__construct($configuration, $plugin_id, $plugin_definition);
     $this->migration = $migration;
     $this->eventDispatcher = $event_dispatcher;
     $this->message = new MigrateMessage();
+    $this->migration_plugin_manager = $migration_plugin_manager;
   }
 
   /**
@@ -172,7 +183,8 @@
       $plugin_id,
       $plugin_definition,
       $migration,
-      $container->get('event_dispatcher')
+      $container->get('event_dispatcher'),
+      $container->get('plugin.manager.migration')
     );
   }
 
@@ -931,11 +943,11 @@
   /**
    * {@inheritdoc}
    */
-  public function max() {
+  public function getHighestId() {
     $destination_ids = array_filter(
       $this->migration->getDestinationPlugin()->getIds(),
       function (array $id) {
-        return $id['type'] == 'integer';
+        return $id['type'] === 'integer';
       }
     );
     if (empty($destination_ids)) {
@@ -954,16 +966,12 @@
     // If there's a bundle, it means we have a derived migration and we need to
     // find all the mapping tables from the related derived migrations.
     if ($base_id = substr($migration_id, 0, strpos($migration_id, static::DERIVATIVE_SEPARATOR))) {
-      // @TODO Inject the plugin manager as a dependency.
-      /** @var \Drupal\migrate\Plugin\MigrationPluginManagerInterface $migration_manager */
-      $migration_manager = \Drupal::service('plugin.manager.migration');
-
-      $migrations = $migration_manager->getDefinitions();
+      $migrations = $this->migration_plugin_manager->getDefinitions();
       foreach ($migrations as $migration_id => $migration) {
-        if ($migration['id'] == $base_id) {
+        if ($migration['id'] === $base_id) {
           // Get this derived migration's mapping table and add it to the list
           // of mapping tables to look in for the highest ID.
-          $stub = $migration_manager->createInstance($migration_id);
+          $stub = $this->migration_plugin_manager->createInstance($migration_id);
           $map_tables[$migration_id] = $stub->getIdMap()->mapTableName();
         }
       }
@@ -983,7 +991,7 @@
       $ids[] = $query->execute()->fetchField();
     }
 
-    // Return the highest of the highest IDs.
+    // Return the highest of all the mapped IDs.
     return max($ids);
   }
 
reverted:
--- b/core/modules/migrate/tests/src/Kernel/MigrateTestBase.php
+++ a/core/modules/migrate/tests/src/Kernel/MigrateTestBase.php
@@ -7,6 +7,7 @@
 use Drupal\migrate\MigrateExecutable;
 use Drupal\migrate\MigrateMessageInterface;
 use Drupal\migrate\Plugin\MigrateIdMapInterface;
+use Drupal\migrate\Plugin\Migration;
 use Drupal\migrate\Plugin\MigrationInterface;
 use Drupal\migrate\Row;
 
@@ -46,9 +47,6 @@
    */
   protected $sourceDatabase;
 
-  /**
-   * {@inheritdoc}
-   */
   public static $modules = ['migrate'];
 
   /**
diff -u b/core/modules/migrate_drupal/tests/src/Kernel/d6/MigrateDrupal6AuditIdsTest.php b/core/modules/migrate_drupal/tests/src/Kernel/d6/MigrateDrupal6AuditIdsTest.php
--- b/core/modules/migrate_drupal/tests/src/Kernel/d6/MigrateDrupal6AuditIdsTest.php
+++ b/core/modules/migrate_drupal/tests/src/Kernel/d6/MigrateDrupal6AuditIdsTest.php
@@ -2,17 +2,10 @@
 
 namespace Drupal\Tests\migrate_drupal\Kernel\d6;
 
-use Drupal\aggregator\Entity\Feed;
-use Drupal\aggregator\Entity\Item;
-use Drupal\block_content\Entity\BlockContent;
-use Drupal\comment\Entity\Comment;
-use Drupal\file\Entity\File;
-use Drupal\menu_link_content\Entity\MenuLinkContent;
 use Drupal\KernelTests\FileSystemModuleDiscoveryDataProviderTrait;
 use Drupal\migrate\Audit\IdAuditor;
 use Drupal\node\Entity\Node;
-use Drupal\taxonomy\Entity\Term;
-use Drupal\user\Entity\User;
+use Drupal\Tests\migrate_drupal\Kernel\CreateContentTrait;
 
 /**
  * Tests the migration auditor for ID conflicts.
@@ -22,6 +15,7 @@
 class MigrateDrupal6AuditIdsTest extends MigrateDrupal6TestBase {
 
   use FileSystemModuleDiscoveryDataProviderTrait;
+  use CreateContentTrait;
 
   /**
    * {@inheritdoc}
@@ -125,71 +119,2 @@
 
-  protected function createContent() {
-    // Create an aggregator feed.
-    $feed = Feed::create([
-      'title' => 'feed',
-      'url' => 'http://www.example.com',
-    ]);
-    $feed->save();
-
-    // Create an aggregator feed item.
-    $item = Item::create([
-      'title' => 'feed item',
-      'fid' => $feed->id(),
-      'link' => 'http://www.example.com',
-    ]);
-    $item->save();
-
-    // Create a block content.
-    $block = BlockContent::create([
-      'info' => 'block',
-      'type' => 'block',
-    ]);
-    $block->save();
-
-    // Create a node.
-    $node = Node::create([
-      'type' => 'page',
-      'title' => 'page',
-    ]);
-    $node->save();
-
-    // Create a comment.
-    $comment = Comment::create([
-      'comment_type' => 'comment',
-      'field_name' => 'comment',
-      'entity_type' => 'node',
-      'entity_id' => $node->id(),
-    ]);
-    $comment->save();
-
-    // Create a file.
-    $file = File::create([
-      'uri' => 'public://example.txt',
-    ]);
-    $file->save();
-
-    // Create a menu link.
-    $menu_link = MenuLinkContent::create([
-      'title' => 'menu link',
-      'link' => ['uri' => 'http://www.example.com'],
-      'menu_name' => 'tools',
-    ]);
-    $menu_link->save();
-
-    // Create a taxonomy term.
-    $term = Term::create([
-      'name' => 'term',
-      'vid' => 'term',
-    ]);
-    $term->save();
-
-    // Create a user.
-    $user = User::create([
-      'uid' => 2,
-      'name' => 'user',
-      'mail' => 'user@example.com',
-    ]);
-    $user->save();
-  }
-
 }
diff -u b/core/modules/migrate_drupal/tests/src/Kernel/d7/MigrateDrupal7AuditIdsTest.php b/core/modules/migrate_drupal/tests/src/Kernel/d7/MigrateDrupal7AuditIdsTest.php
--- b/core/modules/migrate_drupal/tests/src/Kernel/d7/MigrateDrupal7AuditIdsTest.php
+++ b/core/modules/migrate_drupal/tests/src/Kernel/d7/MigrateDrupal7AuditIdsTest.php
@@ -2,17 +2,10 @@
 
 namespace Drupal\Tests\migrate_drupal\Kernel\d7;
 
-use Drupal\aggregator\Entity\Feed;
-use Drupal\aggregator\Entity\Item;
-use Drupal\block_content\Entity\BlockContent;
-use Drupal\comment\Entity\Comment;
-use Drupal\file\Entity\File;
-use Drupal\menu_link_content\Entity\MenuLinkContent;
 use Drupal\KernelTests\FileSystemModuleDiscoveryDataProviderTrait;
 use Drupal\migrate\Audit\IdAuditor;
 use Drupal\node\Entity\Node;
-use Drupal\taxonomy\Entity\Term;
-use Drupal\user\Entity\User;
+use Drupal\Tests\migrate_drupal\Kernel\CreateContentTrait;
 
 /**
  * Tests the migration auditor for ID conflicts.
@@ -22,6 +15,7 @@
 class MigrateDrupal7AuditIdsTest extends MigrateDrupal7TestBase {
 
   use FileSystemModuleDiscoveryDataProviderTrait;
+  use CreateContentTrait;
 
   /**
    * {@inheritdoc}
@@ -124,71 +118,2 @@
 
-  protected function createContent() {
-    // Create an aggregator feed.
-    $feed = Feed::create([
-      'title' => 'feed',
-      'url' => 'http://www.example.com',
-    ]);
-    $feed->save();
-
-    // Create an aggregator feed item.
-    $item = Item::create([
-      'title' => 'feed item',
-      'fid' => $feed->id(),
-      'link' => 'http://www.example.com',
-    ]);
-    $item->save();
-
-    // Create a block content.
-    $block = BlockContent::create([
-      'info' => 'block',
-      'type' => 'block',
-    ]);
-    $block->save();
-
-    // Create a node.
-    $node = Node::create([
-      'type' => 'page',
-      'title' => 'page',
-    ]);
-    $node->save();
-
-    // Create a comment.
-    $comment = Comment::create([
-      'comment_type' => 'comment',
-      'field_name' => 'comment',
-      'entity_type' => 'node',
-      'entity_id' => $node->id(),
-    ]);
-    $comment->save();
-
-    // Create a file.
-    $file = File::create([
-      'uri' => 'public://example.txt',
-    ]);
-    $file->save();
-
-    // Create a menu link.
-    $menu_link = MenuLinkContent::create([
-      'title' => 'menu link',
-      'link' => ['uri' => 'http://www.example.com'],
-      'menu_name' => 'tools',
-    ]);
-    $menu_link->save();
-
-    // Create a taxonomy term.
-    $term = Term::create([
-      'name' => 'term',
-      'vid' => 'term',
-    ]);
-    $term->save();
-
-    // Create a user.
-    $user = User::create([
-      'uid' => 2,
-      'name' => 'user',
-      'mail' => 'user@example.com',
-    ]);
-    $user->save();
-  }
-
 }
diff -u b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
--- b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
+++ b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
@@ -8,6 +8,7 @@
 use Drupal\Core\Render\RendererInterface;
 use Drupal\Core\State\StateInterface;
 use Drupal\Core\Url;
+use Drupal\migrate\Audit\AuditorInterface;
 use Drupal\migrate\Audit\IdAuditor;
 use Drupal\migrate\Plugin\migrate\destination\EntityContentBase;
 use Drupal\migrate\Plugin\MigrationPluginManagerInterface;
@@ -51,6 +52,13 @@
   protected $pluginManager;
 
   /**
+   * The auditor service.
+   *
+   * @var \Drupal\migrate\Audit\AuditorInterface
+   */
+  protected $auditor;
+
+  /**
    * Constructs the MigrateUpgradeForm.
    *
    * @param \Drupal\Core\State\StateInterface $state
@@ -61,12 +69,15 @@
    *   The renderer service.
    * @param \Drupal\migrate\Plugin\MigrationPluginManagerInterface $plugin_manager
    *   The migration plugin manager.
+   * @param \Drupal\migrate\Audit\AuditorInterface $auditor
+   *   The auditor service.
    */
-  public function __construct(StateInterface $state, DateFormatterInterface $date_formatter, RendererInterface $renderer, MigrationPluginManagerInterface $plugin_manager) {
+  public function __construct(StateInterface $state, DateFormatterInterface $date_formatter, RendererInterface $renderer, MigrationPluginManagerInterface $plugin_manager, AuditorInterface $auditor) {
     $this->state = $state;
     $this->dateFormatter = $date_formatter;
     $this->renderer = $renderer;
     $this->pluginManager = $plugin_manager;
+    $this->auditor = $auditor;
   }
 
   /**
@@ -77,7 +88,8 @@
       $container->get('state'),
       $container->get('date.formatter'),
       $container->get('renderer'),
-      $container->get('plugin.manager.migration')
+      $container->get('plugin.manager.migration'),
+      $container->get('migrate.audit')
     );
   }
 
@@ -459,10 +471,9 @@
     $migration_ids = array_keys($form_state->get('migrations'));
     $migrations = $this->pluginManager->createInstances($migration_ids);
 
-    $auditor = new IdAuditor();
     $translated_content_conflicts = $content_conflicts = [];
     foreach ($migrations as $migration) {
-      $audit = $auditor->audit($migration);
+      $audit = $this->auditor->audit($migration);
       $destination_plugin = $migration->getDestinationPlugin();
 
       if ($destination_plugin instanceof EntityContentBase && $destination_plugin->isTranslationDestination()) {
diff -u b/core/modules/user/migration_templates/d7_user.yml b/core/modules/user/migration_templates/d7_user.yml
--- b/core/modules/user/migration_templates/d7_user.yml
+++ b/core/modules/user/migration_templates/d7_user.yml
@@ -3,7 +3,7 @@
 audit: true
 migration_tags:
   - Drupal 7
-class: \Drupal\user\Plugin\migrate\User
+class: Drupal\user\Plugin\migrate\User
 source:
   plugin: d7_user
 process:
diff -u b/core/modules/user/src/Plugin/migrate/destination/EntityUser.php b/core/modules/user/src/Plugin/migrate/destination/EntityUser.php
--- b/core/modules/user/src/Plugin/migrate/destination/EntityUser.php
+++ b/core/modules/user/src/Plugin/migrate/destination/EntityUser.php
@@ -130,12 +130,12 @@
   /**
    * {@inheritdoc}
    */
-  public function max() {
-    $highest_id = parent::max();
+  public function getHighestId() {
+    $highest_id = parent::getHighestId();
 
     // Every Drupal site must have a user with UID of 1 and it's normal for
     // migrations to overwrite this user.
-    if ($highest_id == 1) {
+    if ($highest_id === 1) {
       return 0;
     }
     return $highest_id;
only in patch2:
unchanged:
--- a/core/modules/migrate_drupal/migrate_drupal.services.yml
+++ b/core/modules/migrate_drupal/migrate_drupal.services.yml
@@ -16,3 +16,5 @@ services:
       - '@module_handler'
       - '\Drupal\migrate_drupal\Annotation\MigrateCckField'
     deprecated: The "%service_id%" service is deprecated. You should use the 'plugin.manager.migrate.field' service instead. See https://www.drupal.org/node/2751897
+  migrate.audit:
+    class: Drupal\migrate\Audit\IdAuditor
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/migrate_drupal/tests/src/Kernel/CreateContentTrait.php
@@ -0,0 +1,92 @@
+<?php
+
+namespace Drupal\Tests\migrate_drupal\Kernel;
+
+use Drupal\aggregator\Entity\Feed;
+use Drupal\aggregator\Entity\Item;
+use Drupal\block_content\Entity\BlockContent;
+use Drupal\comment\Entity\Comment;
+use Drupal\file\Entity\File;
+use Drupal\menu_link_content\Entity\MenuLinkContent;
+use Drupal\node\Entity\Node;
+use Drupal\taxonomy\Entity\Term;
+use Drupal\user\Entity\User;
+
+/**
+ * Provides helper methods for creating content.
+ */
+trait CreateContentTrait {
+
+  /**
+   * Create several pieces of generic content.
+   */
+  protected function createContent() {
+    // Create an aggregator feed.
+    $feed = Feed::create([
+      'title' => 'feed',
+      'url' => 'http://www.example.com',
+    ]);
+    $feed->save();
+
+    // Create an aggregator feed item.
+    $item = Item::create([
+      'title' => 'feed item',
+      'fid' => $feed->id(),
+      'link' => 'http://www.example.com',
+    ]);
+    $item->save();
+
+    // Create a block content.
+    $block = BlockContent::create([
+      'info' => 'block',
+      'type' => 'block',
+    ]);
+    $block->save();
+
+    // Create a node.
+    $node = Node::create([
+      'type' => 'page',
+      'title' => 'page',
+    ]);
+    $node->save();
+
+    // Create a comment.
+    $comment = Comment::create([
+      'comment_type' => 'comment',
+      'field_name' => 'comment',
+      'entity_type' => 'node',
+      'entity_id' => $node->id(),
+    ]);
+    $comment->save();
+
+    // Create a file.
+    $file = File::create([
+      'uri' => 'public://example.txt',
+    ]);
+    $file->save();
+
+    // Create a menu link.
+    $menu_link = MenuLinkContent::create([
+      'title' => 'menu link',
+      'link' => ['uri' => 'http://www.example.com'],
+      'menu_name' => 'tools',
+    ]);
+    $menu_link->save();
+
+    // Create a taxonomy term.
+    $term = Term::create([
+      'name' => 'term',
+      'vid' => 'term',
+    ]);
+    $term->save();
+
+    // Create a user.
+    $user = User::create([
+      'uid' => 2,
+      'name' => 'user',
+      'mail' => 'user@example.com',
+    ]);
+    $user->save();
+  }
+
+}