--- /dev/null
+<?php
+
+/**
+ * @file
+ * Partial database to mimic the installation of the update_test_schema module.
+ */
+
+use Drupal\Core\Database\Database;
+
+$connection = Database::getConnection();
+
+// Create the table.
+$connection->schema()->createTable('update_test_schema_table', [
+ 'fields' => [
+ 'a' => [
+ 'type' => 'int',
+ 'not null' => TRUE,
+ 'size' => 'normal',
+ ],
+ 'b' => [
+ 'type' => 'blob',
+ 'not null' => FALSE,
+ 'size' => 'normal',
+ ],
+ ],
+]);
+
+// Set the schema version.
+$connection->merge('key_value')
+ ->condition('collection', 'system.schema')
+ ->condition('name', 'update_test_schema')
+ ->fields([
+ 'collection' => 'system.schema',
+ 'name' => 'update_test_schema',
+ 'value' => 'i:8000;',
+ ])
+ ->execute();
+
+// Update core.extension.
+$extensions = $connection->select('config')
+ ->fields('config', ['data'])
+ ->condition('collection', '')
+ ->condition('name', 'core.extension')
+ ->execute()
+ ->fetchField();
+$extensions = unserialize($extensions);
+$extensions['module']['update_test_schema'] = 8000;
+$connection->update('config')
+ ->fields([
+ 'data' => serialize($extensions),
+ ])
+ ->condition('collection', '')
+ ->condition('name', 'core.extension')
+ ->execute();