diff --git a/core/modules/migrate/src/MigrationStorage.php b/core/modules/migrate/src/MigrationStorage.php
deleted file mode 100644
index 282b0c9414ce5e7ad043d0bb750a633ad9f38bef..0000000000000000000000000000000000000000
--- a/core/modules/migrate/src/MigrationStorage.php
+++ /dev/null
@@ -1,187 +0,0 @@
-<?php
-
-namespace Drupal\migrate;
-
-use Drupal\Component\Graph\Graph;
-use Drupal\Component\Uuid\UuidInterface;
-use Drupal\Core\Config\ConfigFactoryInterface;
-use Drupal\Core\Config\Entity\ConfigEntityStorage;
-use Drupal\Core\Entity\EntityTypeInterface;
-use Drupal\Core\Entity\Query\QueryFactoryInterface;
-use Drupal\Core\Language\LanguageManagerInterface;
-use Symfony\Component\DependencyInjection\ContainerInterface;
-
-/**
- * Storage for migration entities.
- */
-class MigrationStorage extends ConfigEntityStorage implements MigrateBuildDependencyInterface {
-
-  /**
-   * The entity query factory service.
-   *
-   * @var \Drupal\Core\Entity\Query\QueryFactoryInterface
-   */
-  protected $queryFactory;
-
-  /**
-   * Constructs a MigrationStorage object.
-   *
-   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
-   *   An entity type definition.
-   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
-   *   The config factory service.
-   * @param \Drupal\Component\Uuid\UuidInterface $uuid_service
-   *   The UUID service.
-   * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
-   *   The language manager.
-   * @param \Drupal\Core\Entity\Query\QueryFactoryInterface $query_factory
-   *   The entity query factory service.
-   */
-  public function __construct(EntityTypeInterface $entity_type, ConfigFactoryInterface $config_factory, UuidInterface $uuid_service, LanguageManagerInterface $language_manager, QueryFactoryInterface $query_factory) {
-    parent::__construct($entity_type, $config_factory, $uuid_service, $language_manager);
-    $this->queryFactory = $query_factory;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public static function createInstance(ContainerInterface $container, EntityTypeInterface $entity_type) {
-    return new static(
-      $entity_type,
-      $container->get('config.factory'),
-      $container->get('uuid'),
-      $container->get('language_manager'),
-      $container->get('entity.query.config')
-    );
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function loadMultiple(array $ids = NULL) {
-    if ($ids) {
-      $ids = $this->getVariantIds($ids);
-    }
-    /** @var \Drupal\migrate\Plugin\MigrationInterface[] $migrations */
-    $migrations = parent::loadMultiple($ids);
-
-    foreach ($migrations as $migration) {
-      $dependencies = array_map([$this, 'getVariantIds'], $migration->getMigrationDependencies());
-      $migration->set('migration_dependencies', $dependencies);
-    }
-
-    // Build an array of dependencies and set the order of the migrations.
-    return $this->buildDependencyMigration($migrations, []);
-  }
-
-  /**
-   * Splices variant IDs into a list of migration IDs.
-   *
-   * IDs which match the template_id:* pattern are shorthand for every variant
-   * of template_id. This method queries for those variant IDs and splices them
-   * into the original list.
-   *
-   * @param string[] $ids
-   *   A set of migration IDs.
-   *
-   * @return string[]
-   *   The expanded list of IDs.
-   */
-  public function getVariantIds(array $ids) {
-    // Re-index the array numerically, since we need to limit the loop by size.
-    $ids = array_values($ids);
-
-    $index = 0;
-    while ($index < count($ids)) {
-      if (substr($ids[$index], -2) == ':*') {
-        $template_id = substr($ids[$index], 0, -2);
-        $variants = $this->queryFactory->get($this->entityType, 'OR')
-          ->condition('id', $template_id)
-          ->condition('template', $template_id)
-          ->execute();
-        array_splice($ids, $index, 1, $variants);
-        $index += count($variants);
-      }
-      else {
-        $index++;
-      }
-    }
-    return $ids;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function buildDependencyMigration(array $migrations, array $dynamic_ids) {
-    // Migration dependencies defined in the migration storage can be
-    // optional or required. If an optional dependency does not run, the current
-    // migration is still OK to go. Both optional and required dependencies
-    // (if run at all) must run before the current migration.
-    $dependency_graph = array();
-    $requirement_graph = array();
-    $different = FALSE;
-    foreach ($migrations as $migration) {
-      /** @var \Drupal\migrate\Plugin\MigrationInterface $migration */
-      $id = $migration->id();
-      $requirements[$id] = array();
-      $dependency_graph[$id]['edges'] = array();
-      $migration_dependencies = $migration->getMigrationDependencies();
-
-      if (isset($migration_dependencies['required'])) {
-        foreach ($migration_dependencies['required'] as $dependency) {
-          if (!isset($dynamic_ids[$dependency])) {
-            $this->addDependency($requirement_graph, $id, $dependency, $dynamic_ids);
-          }
-          $this->addDependency($dependency_graph, $id, $dependency, $dynamic_ids);
-        }
-      }
-      if (isset($migration_dependencies['optional'])) {
-        foreach ($migration_dependencies['optional'] as $dependency) {
-          $different = TRUE;
-          $this->addDependency($dependency_graph, $id, $dependency, $dynamic_ids);
-        }
-      }
-    }
-    $graph_object = new Graph($dependency_graph);
-    $dependency_graph = $graph_object->searchAndSort();
-    if ($different) {
-      $graph_object = new Graph($requirement_graph);
-      $requirement_graph = $graph_object->searchAndSort();
-    }
-    else {
-      $requirement_graph = $dependency_graph;
-    }
-    $weights = array();
-    foreach ($migrations as $migration_id => $migration) {
-      // Populate a weights array to use with array_multisort later.
-      $weights[] = $dependency_graph[$migration_id]['weight'];
-      if (!empty($requirement_graph[$migration_id]['paths'])) {
-        $migration->set('requirements', $requirement_graph[$migration_id]['paths']);
-      }
-    }
-    array_multisort($weights, SORT_DESC, SORT_NUMERIC, $migrations);
-
-    return $migrations;
-  }
-
-  /**
-   * Add one or more dependencies to a graph.
-   *
-   * @param array $graph
-   *   The graph so far, passed by reference.
-   * @param int $id
-   *   The migration ID.
-   * @param string $dependency
-   *   The dependency string.
-   * @param array $dynamic_ids
-   *   The dynamic ID mapping.
-   */
-  protected function addDependency(array &$graph, $id, $dependency, $dynamic_ids) {
-    $dependencies = isset($dynamic_ids[$dependency]) ? $dynamic_ids[$dependency] : array($dependency);
-    if (!isset($graph[$id]['edges'])) {
-      $graph[$id]['edges'] = array();
-    }
-    $graph[$id]['edges'] += array_combine($dependencies, $dependencies);
-  }
-
-}
diff --git a/core/modules/migrate/tests/src/Unit/MigrationStorageTest.php b/core/modules/migrate/tests/src/Unit/MigrationStorageTest.php
deleted file mode 100644
index 3ff44fae83a6156777d9d7e4c90d06e0823a5ac6..0000000000000000000000000000000000000000
--- a/core/modules/migrate/tests/src/Unit/MigrationStorageTest.php
+++ /dev/null
@@ -1,118 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Tests\migrate\Unit\MigrationStorageTest.
- */
-
-namespace Drupal\Tests\migrate\Unit;
-
-use Drupal\Component\Uuid\UuidInterface;
-use Drupal\Core\Config\ConfigFactoryInterface;
-use Drupal\Core\Entity\EntityTypeInterface;
-use Drupal\Core\Entity\Query\QueryFactoryInterface;
-use Drupal\Core\Entity\Query\QueryInterface;
-use Drupal\Core\Language\LanguageManagerInterface;
-use Drupal\migrate\MigrationStorage;
-use Drupal\Tests\UnitTestCase;
-
-/**
- * @coversDefaultClass \Drupal\migrate\MigrationStorage
- * @group migrate
- */
-class MigrationStorageTest extends UnitTestCase {
-
-  /**
-   * The migration storage.
-   *
-   * @var \Drupal\Tests\migrate\Unit\TestMigrationStorage
-   */
-  protected $storage;
-
-  /**
-   * The storage query.
-   *
-   * @var \Drupal\Core\Entity\Query\QueryInterface|\PHPUnit_Framework_MockObject_MockObject
-   */
-  protected $query;
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function setUp() {
-    $this->query = $this->getMock(QueryInterface::class);
-    $this->query->method('condition')
-      ->willReturnSelf();
-
-    $query_factory = $this->getMock(QueryFactoryInterface::class);
-    $query_factory->method('get')
-      ->willReturn($this->query);
-
-    $this->storage = new TestMigrationStorage(
-      $this->getMock(EntityTypeInterface::class),
-      $this->getMock(ConfigFactoryInterface::class),
-      $this->getMock(UuidInterface::class),
-      $this->getMock(LanguageManagerInterface::class),
-      $query_factory
-    );
-  }
-
-  /**
-   * Tests getVariantIds() when variants exist.
-   *
-   * @covers ::getVariantIds
-   */
-  public function testGetVariantIdsWithVariants() {
-    $this->query->method('execute')
-      ->willReturn(['d6_node__page', 'd6_node__article']);
-
-    $ids = $this->storage->getVariantIds(['d6_node:*', 'd6_user']);
-    $this->assertSame(['d6_node__page', 'd6_node__article', 'd6_user'], $ids);
-  }
-
-  /**
-   * Tests getVariantIds() when no variants exist.
-   *
-   * @covers ::getVariantIds
-   */
-  public function testGetVariantIdsNoVariants() {
-    $this->query->method('execute')
-      ->willReturn([]);
-
-    $ids = $this->storage->getVariantIds(['d6_node:*', 'd6_user']);
-    $this->assertSame(['d6_user'], $ids);
-  }
-
-  /**
-   * Tests getVariantIds().
-   *
-   * This tests getVariantIds() when no variants exist and there are no static
-   * (non-variant) dependencies.
-   *
-   * @covers ::getVariantIds
-   */
-  public function testGetVariantIdsNoVariantsOrStaticDependencies() {
-    $this->query->method('execute')
-      ->willReturn([]);
-
-    $ids = $this->storage->getVariantIds(['d6_node:*', 'd6_node_revision:*']);
-    $this->assertSame([], $ids);
-  }
-
-}
-
-/**
- * Test version of \Drupal\migrate\MigrationStorage.
- *
- * This class exposes protected methods for testing.
- */
-class TestMigrationStorage extends MigrationStorage {
-
-  /**
-   * {@inheritdoc}
-   */
-  public function getVariantIds(array $ids) {
-    return parent::getVariantIds($ids);
-  }
-
-}