--- /dev/null
+<?php
+
+namespace Drupal\system\Tests\Entity\Update;
+
+use Drupal\system\Tests\Update\UpdatePathTestBase;
+
+/**
+ * Tests that a newly-added index is properly created during database updates.
+ *
+ * @group Entity
+ */
+class SqlContentEntityStorageSchemaIndexTest extends UpdatePathTestBase {
+
+ /**
+ * {@inheritdoc}
+ */
+ protected function setDatabaseDumpFiles() {
+ $this->databaseDumpFiles = [
+ __DIR__ . '/../../../../tests/fixtures/update/drupal-8.bare.standard.php.gz',
+ ];
+ }
+
+ /**
+ * Tests entity and field schema database updates and execution order.
+ */
+ public function testIndex() {
+ // The initial Drupal 8 database dump before any updates does not include
+ // the entity ID in the entity field data table indices that were added in
+ // https://www.drupal.org/node/2261669.
+ $this->assertTrue(db_index_exists('node_field_data', 'node__default_langcode'), 'Index node__default_langcode exists prior to running updates.');
+ $this->assertFalse(db_index_exists('node_field_data', 'node__id__default_langcode__langcode'), 'Index node__id__default_langcode__langcode does not exist prior to running updates.');
+ $this->assertFalse(db_index_exists('users_field_data', 'user__id__default_langcode__langcode'), 'Index users__id__default_langcode__langcode does not exist prior to running updates.');
+
+ // Running database updates should update the entity schemata to add the
+ // indices from https://www.drupal.org/node/2261669.
+ $this->runUpdates();
+ $this->assertFalse(db_index_exists('node_field_data', 'node__default_langcode'), 'Index node__default_langcode properly removed.');
+ $this->assertTrue(db_index_exists('node_field_data', 'node__id__default_langcode__langcode'), 'Index node__id__default_langcode__langcode properly created on the node_field_data table.');
+ $this->assertTrue(db_index_exists('users_field_data', 'user__id__default_langcode__langcode'), 'Index users__id__default_langcode__langcode properly created on the user_field_data table.');
+ }
+
+}