Automated tests of farmOS Update module.

modules/core/update/tests/modules/farm_update_test/config/install/farm_update.settings.yml

@@ -0,0 +1,2 @@
+exclude_config:
+  - system.theme

modules/core/update/tests/modules/farm_update_test/farm_update_test.info.yml

@@ -0,0 +1,7 @@
+name: farmOS Update Tests
+description: 'Support module for farmOS Update testing.'
+type: module
+package: Testing
+core_version_requirement: ^9
+dependencies:
+  - farm:farm_update

modules/core/update/tests/modules/farm_update_test/farm_update_test.module

@@ -0,0 +1,13 @@
+<?php
+
+/**
+ * @file
+ * Contains farm_update_test.module.
+ */
+
+/**
+ * Implements hook_farm_update_exclude_config().
+ */
+function farm_update_test_farm_update_exclude_config() {
+  return ['system.file'];
+}

modules/core/update/tests/src/Kernel/FarmUpdateTest.php

@@ -0,0 +1,92 @@
+<?php
+
+namespace Drupal\Tests\farm_update\Kernel;
+
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests for farmOS Update module.
+ *
+ * @group farm
+ */
+class FarmUpdateTest extends KernelTestBase {
+
+  /**
+   * The config factory service.
+   *
+   * @var \Drupal\Core\Config\ConfigFactoryInterface
+   */
+  protected $configFactory;
+
+  /**
+   * The farm update service.
+   *
+   * @var \Drupal\farm_update\FarmUpdateInterface
+   */
+  protected $farmUpdate;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'config_update',
+    'farm_update',
+    'farm_update_test',
+    'system',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->configFactory = \Drupal::service('config.factory');
+    $this->farmUpdate = \Drupal::service('farm.update');
+    $this->installConfig([
+      'farm_update_test',
+      'system',
+    ]);
+  }
+
+  /**
+   * Test farmOS Update module.
+   */
+  public function testFarmUpdate() {
+
+    // Confirm that overridden config gets reverted.
+    $this->farmUpdateTestRevertSetting('system.logging', 'error_level', 'all');
+
+    // Confirm that config excluded via hook_farm_update_exclude_config() does
+    // not get reverted.
+    $this->farmUpdateTestRevertSetting('system.file', 'default_scheme', 'public', TRUE);
+
+    // Confirm that config excluded via farm_update.settings does not get
+    // reverted.
+    $this->farmUpdateTestRevertSetting('system.theme', 'default', 'claro', TRUE);
+  }
+
+  /**
+   * Helper method to test reverting a setting.
+   *
+   * @param string $config
+   *   Configuration name.
+   * @param string $setting
+   *   Setting name within the configuration.
+   * @param string $override
+   *   Value to use for override.
+   * @param bool $excluded
+   *   Whether or not we expect this config to be excluded. Defaults to FALSE.
+   *   If set to TRUE, then we expect that the config will still be overridden
+   *   after rebuild.
+   */
+  protected function farmUpdateTestRevertSetting(string $config, string $setting, string $override, bool $excluded = FALSE) {
+    $original = \Drupal::config($config)->get($setting);
+    $this->configFactory->getEditable($config)->set($setting, $override)->save();
+    $this->assertEquals($override, \Drupal::config($config)->get($setting), 'Setting is overridden before rebuild.');
+    $this->farmUpdate->rebuild();
+    $expected_value = $excluded ? $override : $original;
+    $expected_message = $excluded ? 'Setting is overridden after rebuild.' : 'Setting is reverted after rebuild.';
+    $this->assertEquals($expected_value, \Drupal::config($config)->get($setting), $expected_message);
+  }
+
+}