only in patch2:
unchanged:
--- a/core/modules/system/src/Tests/Database/SchemaTest.php
+++ b/core/modules/system/src/Tests/Database/SchemaTest.php
@@ -10,6 +10,7 @@
 use Drupal\Core\Database\Database;
 use Drupal\Core\Database\SchemaObjectDoesNotExistException;
 use Drupal\Core\Database\SchemaObjectExistsException;
+use Drupal\Component\Utility\Unicode;
 use Drupal\simpletest\UnitTestBase;
 
 /**
@@ -30,7 +31,7 @@ class SchemaTest extends UnitTestBase {
   function testSchema() {
     // Try creating a table.
     $table_specification = array(
-      'description' => 'Schema table description.',
+      'description' => 'Schema table description may contain "quotes" and could be long—very long indeed.',
       'fields' => array(
         'id'  => array(
           'type' => 'int',
@@ -39,7 +40,7 @@ function testSchema() {
         'test_field'  => array(
           'type' => 'int',
           'not null' => TRUE,
-          'description' => 'Schema column description.',
+          'description' => 'Schema table description may contain "quotes" and could be long—very long indeed. There could be "multiple quoted regions".',
         ),
         'test_field_string'  => array(
           'type' => 'varchar',
@@ -212,6 +213,13 @@ function tryInsert($table = 'test_table') {
   function checkSchemaComment($description, $table, $column = NULL) {
     if (method_exists(Database::getConnection()->schema(), 'getComment')) {
       $comment = Database::getConnection()->schema()->getComment($table, $column);
+      $db_type = Database::getConnection()->databaseType();
+      // The schema comment truncation for mysql is different.
+      if ($db_type == 'mysql') {
+        $max_length = $column ? 255 : 60;
+        $description = Unicode::truncate($description, $max_length, TRUE, TRUE);
+        $this->assertFalse(0, $description);
+      }
       $this->assertEqual($comment, $description, 'The comment matches the schema description.');
     }
   }