only in patch2:
unchanged:
--- a/core/modules/block/src/Tests/Update/BlockContextMappingUpdateTest.php
+++ b/core/modules/block/src/Tests/Update/BlockContextMappingUpdateTest.php
@@ -107,4 +107,12 @@ public function testUpdateHookN() {
     $this->assertResponse('200');
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected function runUpdates() {
+    parent::runUpdates();
+    $this->fixPreBeta13Schema();
+  }
+
 }
only in patch2:
unchanged:
--- a/core/modules/system/src/Tests/Entity/Update/SqlContentEntityStorageSchemaIndexTest.php
+++ b/core/modules/system/src/Tests/Entity/Update/SqlContentEntityStorageSchemaIndexTest.php
@@ -45,15 +45,15 @@ public function testIndex() {
     $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 automatically update the entity schemata
-    // to add the indices from https://www.drupal.org/node/2261669.
+    // 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.');
 
-    // Ensure that hook_update_N() implementations were in the expected order
-    // relative to the entity and field updates. The expected order is:
+    // Ensure that entity schemata updates were performed in the expected
+    // order, which is:
     // 1. Initial Drupal 8.0.0-beta12 installation with no indices.
     // 2. update_order_test_update_8001() is invoked.
     // 3. update_order_test_update_8002() is invoked.
@@ -61,9 +61,9 @@ public function testIndex() {
     //    the update_order_test_field storage. See update_order_test.module.
     // 5. update_order_test_update_8002() explicitly applies the updates for
     //    the node entity type indices listed above.
-    // 6. The remaining entity schema updates are applied automatically after
-    //    all update hook implementations have run, which applies the user
-    //    index update.
+    // 6. \Drupal\system\Tests\Update\UpdatePathTestBase::fixPreBeta13Schema()
+    //    applies all remaining entity and field updates, which includes the
+    //    user index update.
    $this->assertTrue(\Drupal::state()->get('update_order_test_update_8001', FALSE), 'Index node__default_langcode still existed during update_order_test_update_8001(), indicating that it ran before the entity type updates.');
 
     // Node updates were run during update_order_test_update_8002().
@@ -79,4 +79,12 @@ public function testIndex() {
     $this->assertFalse(\Drupal::state()->get('update_order_test_update_8002_user__id__default_langcode__langcode', TRUE));
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected function runUpdates() {
+    parent::runUpdates();
+    $this->fixPreBeta13Schema();
+  }
+
 }
only in patch2:
unchanged:
--- a/core/modules/system/src/Tests/Update/UpdatePathTestBase.php
+++ b/core/modules/system/src/Tests/Update/UpdatePathTestBase.php
@@ -200,6 +200,26 @@ protected function runUpdates() {
   }
 
   /**
+   * Helper function to fix the schema of pre-beta-13 fixtures.
+   *
+   * Between beta-12 and beta-13, some hook_update_N() functions were added,
+   * with corresponding test coverage, but a beta to beta upgrade path was not
+   * yet officially supported. After beta-13, automated entity and field
+   * schema updates were removed in favor of modules explicitly controlling
+   * which changes to update when. Update tests added after beta-13 should
+   * start with a beta-13 database fixture, but tests that still use a beta-12
+   * fixture can extend the runUpdates() function to invoke this function in
+   * order to emulate what would have happened in a beta-12 to beta-13 update.
+   *
+   * @see \Drupal\block\Tests\Update\BlockContextMappingUpdateTest::runUpdates()
+   * @see \Drupal\system\Tests\Entity\Update\SqlContentEntityStorageSchemaIndexTest::runUpdates()
+   * @see https://www.drupal.org/node/2542748
+   */
+  protected function fixPreBeta13Schema() {
+    \Drupal::service('entity.definition_update_manager')->applyUpdates();
+  }
+
+  /**
    * {@inheritdoc}
    */
   protected function rebuildAll() {
only in patch2:
unchanged:
--- a/core/modules/system/tests/modules/update_order_test/update_order_test.install
+++ b/core/modules/system/tests/modules/update_order_test/update_order_test.install
@@ -15,16 +15,14 @@
 if (\Drupal::state()->get('update_order_test', FALSE)) {
 
   /**
-   * Runs before entity schema updates.
+   * Stores whether the node__default_langcode index exists.
    */
   function update_order_test_update_8001() {
-    // Store whether the node__default_langcode index exists when this hook is
-    // invoked.
     \Drupal::state()->set('update_order_test_update_8001', db_index_exists('node_field_data', 'node__default_langcode'));
   }
 
   /**
-   * Runs before entity schema updates.
+   * Applies some entity schema updates in a specific order.
    */
   function update_order_test_update_8002() {
     // Check and store whether the update_order_test field exists when this