test: Fix overwriting and restoring config values

Assisted-by: ClaudeCode:claude-opus-5
Signed-off-by: Marcel Müller <marcel-mueller@gmx.de>

apps/settings/tests/UserMigration/AccountMigratorTest.php

@@ -13,9 +13,7 @@ use OCA\Settings\UserMigration\AccountMigrator;
 use OCP\Accounts\IAccountManager;
 use OCP\AppFramework\App;
 use OCP\IAvatarManager;
-use OCP\IConfig;
 use OCP\IUserManager;
-use OCP\Server;
 use OCP\UserMigration\IExportDestination;
 use OCP\UserMigration\IImportSource;
 use PHPUnit\Framework\Constraint\JsonMatches;
@@ -46,7 +44,7 @@ class AccountMigratorTest extends TestCase {
 
 		$app = new App(Application::APP_ID);
 		$container = $app->getContainer();
-		$container->get(IConfig::class)->setSystemValue('has_internet_connection', false);
+		$this->overwriteSystemConfig('has_internet_connection', false);
 
 		$this->userManager = $container->get(IUserManager::class);
 		$this->avatarManager = $container->get(IAvatarManager::class);
@@ -57,11 +55,6 @@ class AccountMigratorTest extends TestCase {
 		$this->output = $this->createMock(OutputInterface::class);
 	}
 
-	protected function tearDown(): void {
-		Server::get(IConfig::class)->setSystemValue('has_internet_connection', true);
-		parent::tearDown();
-	}
-
 	public static function dataImportExportAccount(): array {
 		return array_map(
 			static function (string $filename): array {

tests/lib/TestCase.php

@@ -47,10 +47,13 @@ abstract class TestCase extends \PHPUnit\Framework\TestCase {
 	/** @psalm-suppress ImpureStaticProperty */
 	private static bool $wasDatabaseAllowed = false;
 	protected array $services = [];
+	/** Original values keyed by config key; null means the key was unset. */
+	private array $systemConfigValues = [];
 
 	#[\Override]
 	protected function onNotSuccessfulTest(\Throwable $t): never {
 		$this->restoreAllServices();
+		$this->restoreAllSystemConfig();
 
 		// restore database connection
 		if (!$this->IsDatabaseAccessAllowed()) {
@@ -114,6 +117,39 @@ abstract class TestCase extends \PHPUnit\Framework\TestCase {
 		}
 	}
 
+	/**
+	 * Sets a system config value for the duration of the test, restoring the
+	 * previous one in tearDown. System config is persisted to config.php, so a
+	 * leaked value would outlive the whole run.
+	 */
+	protected function overwriteSystemConfig(string $key, mixed $value): void {
+		$config = Server::get(IConfig::class);
+
+		if (!array_key_exists($key, $this->systemConfigValues)) {
+			$this->systemConfigValues[$key] = $config->getSystemValue($key, null);
+		}
+
+		$config->setSystemValue($key, $value);
+	}
+
+	public function restoreAllSystemConfig(): void {
+		if ($this->systemConfigValues === []) {
+			return;
+		}
+
+		$config = Server::get(IConfig::class);
+		foreach ($this->systemConfigValues as $key => $value) {
+			// null reads back as the default, so remove the key instead.
+			if ($value === null) {
+				$config->deleteSystemValue($key);
+			} else {
+				$config->setSystemValue($key, $value);
+			}
+		}
+
+		$this->systemConfigValues = [];
+	}
+
 	protected function getTestTraits(): array {
 		$traits = [];
 		$class = $this;
@@ -161,6 +197,7 @@ abstract class TestCase extends \PHPUnit\Framework\TestCase {
 	#[\Override]
 	protected function tearDown(): void {
 		$this->restoreAllServices();
+		$this->restoreAllSystemConfig();
 
 		// restore database connection
 		if (!$this->IsDatabaseAccessAllowed()) {

tests/lib/TestCaseTest.php

@@ -0,0 +1,91 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace Test;
+
+use OCP\IConfig;
+use OCP\Server;
+
+/**
+ * Tests for TestCase::overwriteSystemConfig(). System config is persisted to
+ * config.php, so a value leaked by a test outlives the run and the next one.
+ */
+#[\PHPUnit\Framework\Attributes\Group('DB')]
+class TestCaseTest extends TestCase {
+	private const KEY = 'testcase_overwrite_system_config';
+
+	private IConfig $config;
+
+	#[\Override]
+	protected function setUp(): void {
+		parent::setUp();
+
+		$this->config = Server::get(IConfig::class);
+		$this->config->deleteSystemValue(self::KEY);
+	}
+
+	#[\Override]
+	protected function tearDown(): void {
+		parent::tearDown();
+
+		$this->config->deleteSystemValue(self::KEY);
+	}
+
+	public function testOverwriteSetsTheValue(): void {
+		$this->overwriteSystemConfig(self::KEY, 'overwritten');
+
+		$this->assertSame('overwritten', $this->config->getSystemValue(self::KEY));
+	}
+
+	public function testRestoreRemovesAPreviouslyUnsetKey(): void {
+		$this->overwriteSystemConfig(self::KEY, 'overwritten');
+		$this->restoreAllSystemConfig();
+
+		$this->assertSame('fallback', $this->config->getSystemValue(self::KEY, 'fallback'));
+	}
+
+	public function testRestoreReturnsThePreviousValue(): void {
+		$this->config->setSystemValue(self::KEY, 'original');
+
+		$this->overwriteSystemConfig(self::KEY, 'overwritten');
+		$this->restoreAllSystemConfig();
+
+		$this->assertSame('original', $this->config->getSystemValue(self::KEY));
+	}
+
+	public function testRestoreReturnsThePreviousValueAfterRepeatedOverwrites(): void {
+		$this->config->setSystemValue(self::KEY, 'original');
+
+		$this->overwriteSystemConfig(self::KEY, 'first');
+		$this->overwriteSystemConfig(self::KEY, 'second');
+		$this->restoreAllSystemConfig();
+
+		$this->assertSame('original', $this->config->getSystemValue(self::KEY));
+	}
+
+	public function testRestoreIsIdempotent(): void {
+		$this->config->setSystemValue(self::KEY, 'original');
+
+		$this->overwriteSystemConfig(self::KEY, 'overwritten');
+		$this->restoreAllSystemConfig();
+		$this->config->setSystemValue(self::KEY, 'set afterwards');
+		$this->restoreAllSystemConfig();
+
+		$this->assertSame('set afterwards', $this->config->getSystemValue(self::KEY));
+	}
+
+	/** false is falsy but set: an isset-based check would wrongly delete the key. */
+	public function testRestoreReturnsAPreviousFalseValue(): void {
+		$this->config->setSystemValue(self::KEY, false);
+
+		$this->overwriteSystemConfig(self::KEY, true);
+		$this->restoreAllSystemConfig();
+
+		$this->assertFalse($this->config->getSystemValue(self::KEY, 'fallback'));
+	}
+}