diff -u b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
--- b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
+++ b/core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php
@@ -701,6 +701,9 @@
       $this->assertTrue($success, t('Enabled modules: %modules', array('%modules' => implode(', ', $modules))));
     }
 
+    // Reset/rebuild all data structures after enabling the modules.
+    $this->resetAll();
+
     // Use the test mail class instead of the default mail handler class.
     variable_set('mail_system', array('default-system' => 'Drupal\Core\Mail\VariableLog'));
 
only in patch2:
unchanged:
--- a/core/modules/block/block.install
+++ b/core/modules/block/block.install
@@ -74,7 +74,8 @@ function block_schema() {
       ),
       'pages' => array(
         'type' => 'text',
-        'not null' => TRUE,
+        // @todo Block module saves empty strings instead of NULL.
+        'not null' => FALSE,
         'description' => 'Contents of the "Pages" block; contains either a list of paths on which to include/exclude the block or PHP code, depending on "visibility" setting.',
       ),
       'title' => array(
@@ -312,6 +313,17 @@ function block_update_8002() {
 }
 
 /**
+ * Make {block}.pages optional.
+ */
+function block_update_8003() {
+  db_change_field('block', 'pages', 'pages', array(
+    'type' => 'text',
+    'not null' => FALSE,
+    'description' => 'Contents of the "Pages" block; contains either a list of paths on which to include/exclude the block or PHP code, depending on "visibility" setting.',
+  ));
+}
+
+/**
  * @} End of "addtogroup updates-7.x-to-8.x".
  * The next series of updates should start at 9000.
  */