Merge "Don't reset name tables between test runs."

[lhc/web/wiklou.git] / tests / phpunit / MediaWikiTestCase.php

<?php

use MediaWiki\Logger\LegacySpi;
use MediaWiki\Logger\LoggerFactory;
use MediaWiki\Logger\MonologSpi;
use MediaWiki\MediaWikiServices;
use Psr\Log\LoggerInterface;
use Wikimedia\Rdbms\IDatabase;
use Wikimedia\Rdbms\IMaintainableDatabase;
use Wikimedia\Rdbms\Database;
use Wikimedia\Rdbms\IResultWrapper;
use Wikimedia\Rdbms\LBFactory;
use Wikimedia\TestingAccessWrapper;

/**
 * @since 1.18
 */
abstract class MediaWikiTestCase extends PHPUnit\Framework\TestCase {

        use MediaWikiCoversValidator;
        use PHPUnit4And6Compat;

        /**
         * The service locator created by prepareServices(). This service locator will
         * be restored after each test. Tests that pollute the global service locator
         * instance should use overrideMwServices() to isolate the test.
         *
         * @var MediaWikiServices|null
         */
        private static $serviceLocator = null;

        /**
         * $called tracks whether the setUp and tearDown method has been called.
         * class extending MediaWikiTestCase usually override setUp and tearDown
         * but forget to call the parent.
         *
         * The array format takes a method name as key and anything as a value.
         * By asserting the key exist, we know the child class has called the
         * parent.
         *
         * This property must be private, we do not want child to override it,
         * they should call the appropriate parent method instead.
         */
        private $called = [];

        /**
         * @var TestUser[]
         * @since 1.20
         */
        public static $users;

        /**
         * Primary database
         *
         * @var Database
         * @since 1.18
         */
        protected $db;

        /**
         * @var array
         * @since 1.19
         */
        protected $tablesUsed = []; // tables with data

        private static $useTemporaryTables = true;
        private static $reuseDB = false;
        private static $dbSetup = false;
        private static $oldTablePrefix = '';

        /**
         * Original value of PHP's error_reporting setting.
         *
         * @var int
         */
        private $phpErrorLevel;

        /**
         * Holds the paths of temporary files/directories created through getNewTempFile,
         * and getNewTempDirectory
         *
         * @var array
         */
        private $tmpFiles = [];

        /**
         * Holds original values of MediaWiki configuration settings
         * to be restored in tearDown().
         * See also setMwGlobals().
         * @var array
         */
        private $mwGlobals = [];

        /**
         * Holds list of MediaWiki configuration settings to be unset in tearDown().
         * See also setMwGlobals().
         * @var array
         */
        private $mwGlobalsToUnset = [];

        /**
         * Holds original contents of interwiki table
         * @var IResultWrapper
         */
        private $interwikiTable = null;

        /**
         * Holds original loggers which have been replaced by setLogger()
         * @var LoggerInterface[]
         */
        private $loggers = [];

        /**
         * Table name prefixes. Oracle likes it shorter.
         */
        const DB_PREFIX = 'unittest_';
        const ORA_DB_PREFIX = 'ut_';

        /**
         * @var array
         * @since 1.18
         */
        protected $supportedDBs = [
                'mysql',
                'sqlite',
                'postgres',
                'oracle'
        ];

        public function __construct( $name = null, array $data = [], $dataName = '' ) {
                parent::__construct( $name, $data, $dataName );

                $this->backupGlobals = false;
                $this->backupStaticAttributes = false;
        }

        public function __destruct() {
                // Complain if self::setUp() was called, but not self::tearDown()
                // $this->called['setUp'] will be checked by self::testMediaWikiTestCaseParentSetupCalled()
                if ( isset( $this->called['setUp'] ) && !isset( $this->called['tearDown'] ) ) {
                        throw new MWException( static::class . "::tearDown() must call parent::tearDown()" );
                }
        }

        public static function setUpBeforeClass() {
                parent::setUpBeforeClass();

                // Get the service locator, and reset services if it's not done already
                self::$serviceLocator = self::prepareServices( new GlobalVarConfig() );
        }

        /**
         * Convenience method for getting an immutable test user
         *
         * @since 1.28
         *
         * @param string[] $groups Groups the test user should be in.
         * @return TestUser
         */
        public static function getTestUser( $groups = [] ) {
                return TestUserRegistry::getImmutableTestUser( $groups );
        }

        /**
         * Convenience method for getting a mutable test user
         *
         * @since 1.28
         *
         * @param string[] $groups Groups the test user should be added in.
         * @return TestUser
         */
        public static function getMutableTestUser( $groups = [] ) {
                return TestUserRegistry::getMutableTestUser( __CLASS__, $groups );
        }

        /**
         * Convenience method for getting an immutable admin test user
         *
         * @since 1.28
         *
         * @param string[] $groups Groups the test user should be added to.
         * @return TestUser
         */
        public static function getTestSysop() {
                return self::getTestUser( [ 'sysop', 'bureaucrat' ] );
        }

        /**
         * Returns a WikiPage representing an existing page.
         *
         * @since 1.32
         *
         * @param Title|string|null $title
         * @return WikiPage
         * @throws MWException
         */
        protected function getExistingTestPage( $title = null ) {
                $title = ( $title === null ) ? 'UTPage' : $title;
                $title = is_string( $title ) ? Title::newFromText( $title ) : $title;
                $page = WikiPage::factory( $title );

                if ( !$page->exists() ) {
                        $user = self::getTestSysop()->getUser();
                        $page->doEditContent(
                                new WikitextContent( 'UTContent' ),
                                'UTPageSummary',
                                EDIT_NEW | EDIT_SUPPRESS_RC,
                                false,
                                $user
                        );
                }

                return $page;
        }

        /**
         * Returns a WikiPage representing a non-existing page.
         *
         * @since 1.32
         *
         * @param Title|string|null $title
         * @return WikiPage
         * @throws MWException
         */
        protected function getNonexistingTestPage( $title = null ) {
                $title = ( $title === null ) ? 'UTPage-' . rand( 0, 100000 ) : $title;
                $title = is_string( $title ) ? Title::newFromText( $title ) : $title;
                $page = WikiPage::factory( $title );

                if ( $page->exists() ) {
                        $page->doDeleteArticle( 'Testing' );
                }

                return $page;
        }

        /**
         * Prepare service configuration for unit testing.
         *
         * This calls MediaWikiServices::resetGlobalInstance() to allow some critical services
         * to be overridden for testing.
         *
         * prepareServices() only needs to be called once, but should be called as early as possible,
         * before any class has a chance to grab a reference to any of the global services
         * instances that get discarded by prepareServices(). Only the first call has any effect,
         * later calls are ignored.
         *
         * @note This is called by PHPUnitMaintClass::finalSetup.
         *
         * @see MediaWikiServices::resetGlobalInstance()
         *
         * @param Config $bootstrapConfig The bootstrap config to use with the new
         *        MediaWikiServices. Only used for the first call to this method.
         * @return MediaWikiServices
         */
        public static function prepareServices( Config $bootstrapConfig ) {
                static $services = null;

                if ( !$services ) {
                        $services = self::resetGlobalServices( $bootstrapConfig );
                }
                return $services;
        }

        /**
         * Reset global services, and install testing environment.
         * This is the testing equivalent of MediaWikiServices::resetGlobalInstance().
         * This should only be used to set up the testing environment, not when
         * running unit tests. Use MediaWikiTestCase::overrideMwServices() for that.
         *
         * @see MediaWikiServices::resetGlobalInstance()
         * @see prepareServices()
         * @see MediaWikiTestCase::overrideMwServices()
         *
         * @param Config|null $bootstrapConfig The bootstrap config to use with the new
         *        MediaWikiServices.
         * @return MediaWikiServices
         */
        private static function resetGlobalServices( Config $bootstrapConfig = null ) {
                $oldServices = MediaWikiServices::getInstance();
                $oldConfigFactory = $oldServices->getConfigFactory();
                $oldLoadBalancerFactory = $oldServices->getDBLoadBalancerFactory();

                $testConfig = self::makeTestConfig( $bootstrapConfig );

                MediaWikiServices::resetGlobalInstance( $testConfig );

                $serviceLocator = MediaWikiServices::getInstance();
                self::installTestServices(
                        $oldConfigFactory,
                        $oldLoadBalancerFactory,
                        $serviceLocator
                );
                return $serviceLocator;
        }

        /**
         * Create a config suitable for testing, based on a base config, default overrides,
         * and custom overrides.
         *
         * @param Config|null $baseConfig
         * @param Config|null $customOverrides
         *
         * @return Config
         */
        private static function makeTestConfig(
                Config $baseConfig = null,
                Config $customOverrides = null
        ) {
                $defaultOverrides = new HashConfig();

                if ( !$baseConfig ) {
                        $baseConfig = MediaWikiServices::getInstance()->getBootstrapConfig();
                }

                /* Some functions require some kind of caching, and will end up using the db,
                 * which we can't allow, as that would open a new connection for mysql.
                 * Replace with a HashBag. They would not be going to persist anyway.
                 */
                $hashCache = [ 'class' => HashBagOStuff::class, 'reportDupes' => false ];
                $objectCaches = [
                                CACHE_DB => $hashCache,
                                CACHE_ACCEL => $hashCache,
                                CACHE_MEMCACHED => $hashCache,
                                'apc' => $hashCache,
                                'apcu' => $hashCache,
                                'wincache' => $hashCache,
                        ] + $baseConfig->get( 'ObjectCaches' );

                $defaultOverrides->set( 'ObjectCaches', $objectCaches );
                $defaultOverrides->set( 'MainCacheType', CACHE_NONE );
                $defaultOverrides->set( 'JobTypeConf', [ 'default' => [ 'class' => JobQueueMemory::class ] ] );

                // Use a fast hash algorithm to hash passwords.
                $defaultOverrides->set( 'PasswordDefault', 'A' );

                $testConfig = $customOverrides
                        ? new MultiConfig( [ $customOverrides, $defaultOverrides, $baseConfig ] )
                        : new MultiConfig( [ $defaultOverrides, $baseConfig ] );

                return $testConfig;
        }

        /**
         * @param ConfigFactory $oldConfigFactory
         * @param LBFactory $oldLoadBalancerFactory
         * @param MediaWikiServices $newServices
         *
         * @throws MWException
         */
        private static function installTestServices(
                ConfigFactory $oldConfigFactory,
                LBFactory $oldLoadBalancerFactory,
                MediaWikiServices $newServices
        ) {
                // Use bootstrap config for all configuration.
                // This allows config overrides via global variables to take effect.
                $bootstrapConfig = $newServices->getBootstrapConfig();
                $newServices->resetServiceForTesting( 'ConfigFactory' );
                $newServices->redefineService(
                        'ConfigFactory',
                        self::makeTestConfigFactoryInstantiator(
                                $oldConfigFactory,
                                [ 'main' => $bootstrapConfig ]
                        )
                );
                $newServices->resetServiceForTesting( 'DBLoadBalancerFactory' );
                $newServices->redefineService(
                        'DBLoadBalancerFactory',
                        function ( MediaWikiServices $services ) use ( $oldLoadBalancerFactory ) {
                                return $oldLoadBalancerFactory;
                        }
                );
        }

        /**
         * @param ConfigFactory $oldFactory
         * @param Config[] $configurations
         *
         * @return Closure
         */
        private static function makeTestConfigFactoryInstantiator(
                ConfigFactory $oldFactory,
                array $configurations
        ) {
                return function ( MediaWikiServices $services ) use ( $oldFactory, $configurations ) {
                        $factory = new ConfigFactory();

                        // clone configurations from $oldFactory that are not overwritten by $configurations
                        $namesToClone = array_diff(
                                $oldFactory->getConfigNames(),
                                array_keys( $configurations )
                        );

                        foreach ( $namesToClone as $name ) {
                                $factory->register( $name, $oldFactory->makeConfig( $name ) );
                        }

                        foreach ( $configurations as $name => $config ) {
                                $factory->register( $name, $config );
                        }

                        return $factory;
                };
        }

        /**
         * Resets some well known services that typically have state that may interfere with unit tests.
         * This is a lightweight alternative to resetGlobalServices().
         *
         * @note There is no guarantee that no references remain to stale service instances destroyed
         * by a call to doLightweightServiceReset().
         *
         * @throws MWException if called outside of PHPUnit tests.
         *
         * @see resetGlobalServices()
         */
        private function doLightweightServiceReset() {
                global $wgRequest, $wgJobClasses;

                foreach ( $wgJobClasses as $type => $class ) {
                        JobQueueGroup::singleton()->get( $type )->delete();
                }
                JobQueueGroup::destroySingletons();

                ObjectCache::clear();
                $services = MediaWikiServices::getInstance();
                $services->resetServiceForTesting( 'MainObjectStash' );
                $services->resetServiceForTesting( 'LocalServerObjectCache' );
                $services->getMainWANObjectCache()->clearProcessCache();
                FileBackendGroup::destroySingleton();
                DeferredUpdates::clearPendingUpdates();

                // TODO: move global state into MediaWikiServices
                RequestContext::resetMain();
                if ( session_id() !== '' ) {
                        session_write_close();
                        session_id( '' );
                }

                $wgRequest = new FauxRequest();
                MediaWiki\Session\SessionManager::resetCache();
        }

        public function run( PHPUnit_Framework_TestResult $result = null ) {
                $needsResetDB = false;

                if ( !self::$dbSetup || $this->needsDB() ) {
                        // set up a DB connection for this test to use

                        self::$useTemporaryTables = !$this->getCliArg( 'use-normal-tables' );
                        self::$reuseDB = $this->getCliArg( 'reuse-db' );

                        $this->db = wfGetDB( DB_MASTER );

                        $this->checkDbIsSupported();

                        if ( !self::$dbSetup ) {
                                $this->setupAllTestDBs();
                                $this->addCoreDBData();
                        }

                        // TODO: the DB setup should be done in setUpBeforeClass(), so the test DB
                        // is available in subclass's setUpBeforeClass() and setUp() methods.
                        // This would also remove the need for the HACK that is oncePerClass().
                        if ( $this->oncePerClass() ) {
                                $this->setUpSchema( $this->db );
                                $this->resetDB( $this->db, $this->tablesUsed );
                                $this->addDBDataOnce();
                        }

                        $this->addDBData();
                        $needsResetDB = true;
                }

                parent::run( $result );

                if ( $needsResetDB ) {
                        $this->resetDB( $this->db, $this->tablesUsed );
                }
        }

        /**
         * @return bool
         */
        private function oncePerClass() {
                // Remember current test class in the database connection,
                // so we know when we need to run addData.

                $class = static::class;

                $first = !isset( $this->db->_hasDataForTestClass )
                        || $this->db->_hasDataForTestClass !== $class;

                $this->db->_hasDataForTestClass = $class;
                return $first;
        }

        /**
         * @since 1.21
         *
         * @return bool
         */
        public function usesTemporaryTables() {
                return self::$useTemporaryTables;
        }

        /**
         * Obtains a new temporary file name
         *
         * The obtained filename is enlisted to be removed upon tearDown
         *
         * @since 1.20
         *
         * @return string Absolute name of the temporary file
         */
        protected function getNewTempFile() {
                $fileName = tempnam( wfTempDir(), 'MW_PHPUnit_' . static::class . '_' );
                $this->tmpFiles[] = $fileName;

                return $fileName;
        }

        /**
         * obtains a new temporary directory
         *
         * The obtained directory is enlisted to be removed (recursively with all its contained
         * files) upon tearDown.
         *
         * @since 1.20
         *
         * @return string Absolute name of the temporary directory
         */
        protected function getNewTempDirectory() {
                // Starting of with a temporary /file/.
                $fileName = $this->getNewTempFile();

                // Converting the temporary /file/ to a /directory/
                // The following is not atomic, but at least we now have a single place,
                // where temporary directory creation is bundled and can be improved
                unlink( $fileName );
                $this->assertTrue( wfMkdirParents( $fileName ) );

                return $fileName;
        }

        protected function setUp() {
                parent::setUp();
                $this->called['setUp'] = true;

                $this->phpErrorLevel = intval( ini_get( 'error_reporting' ) );

                // Cleaning up temporary files
                foreach ( $this->tmpFiles as $fileName ) {
                        if ( is_file( $fileName ) || ( is_link( $fileName ) ) ) {
                                unlink( $fileName );
                        } elseif ( is_dir( $fileName ) ) {
                                wfRecursiveRemoveDir( $fileName );
                        }
                }

                if ( $this->needsDB() && $this->db ) {
                        // Clean up open transactions
                        while ( $this->db->trxLevel() > 0 ) {
                                $this->db->rollback( __METHOD__, 'flush' );
                        }
                        // Check for unsafe queries
                        if ( $this->db->getType() === 'mysql' ) {
                                $this->db->query( "SET sql_mode = 'STRICT_ALL_TABLES'" );
                        }
                }

                // Store contents of interwiki table in case it changes.  Unfortunately, we seem to have no
                // way to do this only when needed, because tablesUsed can be changed mid-test.
                if ( $this->db ) {
                        $this->interwikiTable = $this->db->select( 'interwiki', '*', '', __METHOD__ );
                }

                // Reset all caches between tests.
                $this->doLightweightServiceReset();

                // XXX: reset maintenance triggers
                // Hook into period lag checks which often happen in long-running scripts
                $services = MediaWikiServices::getInstance();
                $lbFactory = $services->getDBLoadBalancerFactory();
                Maintenance::setLBFactoryTriggers( $lbFactory, $services->getMainConfig() );

                ob_start( 'MediaWikiTestCase::wfResetOutputBuffersBarrier' );
        }

        protected function addTmpFiles( $files ) {
                $this->tmpFiles = array_merge( $this->tmpFiles, (array)$files );
        }

        protected function tearDown() {
                global $wgRequest, $wgSQLMode;

                $status = ob_get_status();
                if ( isset( $status['name'] ) &&
                        $status['name'] === 'MediaWikiTestCase::wfResetOutputBuffersBarrier'
                ) {
                        ob_end_flush();
                }

                $this->called['tearDown'] = true;
                // Cleaning up temporary files
                foreach ( $this->tmpFiles as $fileName ) {
                        if ( is_file( $fileName ) || ( is_link( $fileName ) ) ) {
                                unlink( $fileName );
                        } elseif ( is_dir( $fileName ) ) {
                                wfRecursiveRemoveDir( $fileName );
                        }
                }

                if ( $this->needsDB() && $this->db ) {
                        // Clean up open transactions
                        while ( $this->db->trxLevel() > 0 ) {
                                $this->db->rollback( __METHOD__, 'flush' );
                        }
                        if ( $this->db->getType() === 'mysql' ) {
                                $this->db->query( "SET sql_mode = " . $this->db->addQuotes( $wgSQLMode ) );
                        }
                }

                // Restore mw globals
                foreach ( $this->mwGlobals as $key => $value ) {
                        $GLOBALS[$key] = $value;
                }
                foreach ( $this->mwGlobalsToUnset as $value ) {
                        unset( $GLOBALS[$value] );
                }
                if (
                        array_key_exists( 'wgExtraNamespaces', $this->mwGlobals ) ||
                        in_array( 'wgExtraNamespaces', $this->mwGlobalsToUnset )
                ) {
                        $this->resetNamespaces();
                }
                $this->mwGlobals = [];
                $this->mwGlobalsToUnset = [];
                $this->restoreLoggers();

                if ( self::$serviceLocator && MediaWikiServices::getInstance() !== self::$serviceLocator ) {
                        MediaWikiServices::forceGlobalInstance( self::$serviceLocator );
                }

                // TODO: move global state into MediaWikiServices
                RequestContext::resetMain();
                if ( session_id() !== '' ) {
                        session_write_close();
                        session_id( '' );
                }
                $wgRequest = new FauxRequest();
                MediaWiki\Session\SessionManager::resetCache();
                MediaWiki\Auth\AuthManager::resetCache();

                $phpErrorLevel = intval( ini_get( 'error_reporting' ) );

                if ( $phpErrorLevel !== $this->phpErrorLevel ) {
                        ini_set( 'error_reporting', $this->phpErrorLevel );

                        $oldHex = strtoupper( dechex( $this->phpErrorLevel ) );
                        $newHex = strtoupper( dechex( $phpErrorLevel ) );
                        $message = "PHP error_reporting setting was left dirty: "
                                . "was 0x$oldHex before test, 0x$newHex after test!";

                        $this->fail( $message );
                }

                parent::tearDown();
        }

        /**
         * Make sure MediaWikiTestCase extending classes have called their
         * parent setUp method
         *
         * With strict coverage activated in PHP_CodeCoverage, this test would be
         * marked as risky without the following annotation (T152923).
         * @coversNothing
         */
        final public function testMediaWikiTestCaseParentSetupCalled() {
                $this->assertArrayHasKey( 'setUp', $this->called,
                        static::class . '::setUp() must call parent::setUp()'
                );
        }

        /**
         * Sets a service, maintaining a stashed version of the previous service to be
         * restored in tearDown
         *
         * @since 1.27
         *
         * @param string $name
         * @param object $object
         */
        protected function setService( $name, $object ) {
                // If we did not yet override the service locator, so so now.
                if ( MediaWikiServices::getInstance() === self::$serviceLocator ) {
                        $this->overrideMwServices();
                }

                MediaWikiServices::getInstance()->disableService( $name );
                MediaWikiServices::getInstance()->redefineService(
                        $name,
                        function () use ( $object ) {
                                return $object;
                        }
                );

                if ( $name === 'ContentLanguage' ) {
                        $this->doSetMwGlobals( [ 'wgContLang' => $object ] );
                }
        }

        /**
         * Sets a global, maintaining a stashed version of the previous global to be
         * restored in tearDown
         *
         * The key is added to the array of globals that will be reset afterwards
         * in the tearDown().
         *
         * @par Example
         * @code
         *     protected function setUp() {
         *         $this->setMwGlobals( 'wgRestrictStuff', true );
         *     }
         *
         *     function testFoo() {}
         *
         *     function testBar() {}
         *         $this->assertTrue( self::getX()->doStuff() );
         *
         *         $this->setMwGlobals( 'wgRestrictStuff', false );
         *         $this->assertTrue( self::getX()->doStuff() );
         *     }
         *
         *     function testQuux() {}
         * @endcode
         *
         * @param array|string $pairs Key to the global variable, or an array
         *  of key/value pairs.
         * @param mixed|null $value Value to set the global to (ignored
         *  if an array is given as first argument).
         *
         * @note To allow changes to global variables to take effect on global service instances,
         *       call overrideMwServices().
         *
         * @since 1.21
         */
        protected function setMwGlobals( $pairs, $value = null ) {
                if ( is_string( $pairs ) ) {
                        $pairs = [ $pairs => $value ];
                }

                if ( isset( $pairs['wgContLang'] ) ) {
                        throw new MWException(
                                'No setting $wgContLang, use setContentLang() or setService( \'ContentLanguage\' )'
                        );
                }

                $this->doSetMwGlobals( $pairs, $value );
        }

        /**
         * An internal method that allows setService() to set globals that tests are not supposed to
         * touch.
         */
        private function doSetMwGlobals( $pairs, $value = null ) {
                $this->stashMwGlobals( array_keys( $pairs ) );

                foreach ( $pairs as $key => $value ) {
                        $GLOBALS[$key] = $value;
                }

                if ( array_key_exists( 'wgExtraNamespaces', $pairs ) ) {
                        $this->resetNamespaces();
                }
        }

        /**
         * Must be called whenever namespaces are changed, e.g., $wgExtraNamespaces is altered.
         * Otherwise old namespace data will lurk and cause bugs.
         */
        private function resetNamespaces() {
                MWNamespace::clearCaches();
                Language::clearCaches();

                // We can't have the TitleFormatter holding on to an old Language object either
                // @todo We shouldn't need to reset all the aliases here.
                $services = MediaWikiServices::getInstance();
                $services->resetServiceForTesting( 'TitleFormatter' );
                $services->resetServiceForTesting( 'TitleParser' );
                $services->resetServiceForTesting( '_MediaWikiTitleCodec' );
        }

        /**
         * Check if we can back up a value by performing a shallow copy.
         * Values which fail this test are copied recursively.
         *
         * @param mixed $value
         * @return bool True if a shallow copy will do; false if a deep copy
         *  is required.
         */
        private static function canShallowCopy( $value ) {
                if ( is_scalar( $value ) || $value === null ) {
                        return true;
                }
                if ( is_array( $value ) ) {
                        foreach ( $value as $subValue ) {
                                if ( !is_scalar( $subValue ) && $subValue !== null ) {
                                        return false;
                                }
                        }
                        return true;
                }
                return false;
        }

        /**
         * Stashes the global, will be restored in tearDown()
         *
         * Individual test functions may override globals through the setMwGlobals() function
         * or directly. When directly overriding globals their keys should first be passed to this
         * method in setUp to avoid breaking global state for other tests
         *
         * That way all other tests are executed with the same settings (instead of using the
         * unreliable local settings for most tests and fix it only for some tests).
         *
         * @param array|string $globalKeys Key to the global variable, or an array of keys.
         *
         * @note To allow changes to global variables to take effect on global service instances,
         *       call overrideMwServices().
         *
         * @since 1.23
         */
        protected function stashMwGlobals( $globalKeys ) {
                if ( is_string( $globalKeys ) ) {
                        $globalKeys = [ $globalKeys ];
                }

                foreach ( $globalKeys as $globalKey ) {
                        // NOTE: make sure we only save the global once or a second call to
                        // setMwGlobals() on the same global would override the original
                        // value.
                        if (
                                !array_key_exists( $globalKey, $this->mwGlobals ) &&
                                !array_key_exists( $globalKey, $this->mwGlobalsToUnset )
                        ) {
                                if ( !array_key_exists( $globalKey, $GLOBALS ) ) {
                                        $this->mwGlobalsToUnset[$globalKey] = $globalKey;
                                        continue;
                                }
                                // NOTE: we serialize then unserialize the value in case it is an object
                                // this stops any objects being passed by reference. We could use clone
                                // and if is_object but this does account for objects within objects!
                                if ( self::canShallowCopy( $GLOBALS[$globalKey] ) ) {
                                        $this->mwGlobals[$globalKey] = $GLOBALS[$globalKey];
                                } elseif (
                                        // Many MediaWiki types are safe to clone. These are the
                                        // ones that are most commonly stashed.
                                        $GLOBALS[$globalKey] instanceof Language ||
                                        $GLOBALS[$globalKey] instanceof User ||
                                        $GLOBALS[$globalKey] instanceof FauxRequest
                                ) {
                                        $this->mwGlobals[$globalKey] = clone $GLOBALS[$globalKey];
                                } elseif ( $this->containsClosure( $GLOBALS[$globalKey] ) ) {
                                        // Serializing Closure only gives a warning on HHVM while
                                        // it throws an Exception on Zend.
                                        // Workaround for https://github.com/facebook/hhvm/issues/6206
                                        $this->mwGlobals[$globalKey] = $GLOBALS[$globalKey];
                                } else {
                                        try {
                                                $this->mwGlobals[$globalKey] = unserialize( serialize( $GLOBALS[$globalKey] ) );
                                        } catch ( Exception $e ) {
                                                $this->mwGlobals[$globalKey] = $GLOBALS[$globalKey];
                                        }
                                }
                        }
                }
        }

        /**
         * @param mixed $var
         * @param int $maxDepth
         *
         * @return bool
         */
        private function containsClosure( $var, $maxDepth = 15 ) {
                if ( $var instanceof Closure ) {
                        return true;
                }
                if ( !is_array( $var ) || $maxDepth === 0 ) {
                        return false;
                }

                foreach ( $var as $value ) {
                        if ( $this->containsClosure( $value, $maxDepth - 1 ) ) {
                                return true;
                        }
                }
                return false;
        }

        /**
         * Merges the given values into a MW global array variable.
         * Useful for setting some entries in a configuration array, instead of
         * setting the entire array.
         *
         * @param string $name The name of the global, as in wgFooBar
         * @param array $values The array containing the entries to set in that global
         *
         * @throws MWException If the designated global is not an array.
         *
         * @note To allow changes to global variables to take effect on global service instances,
         *       call overrideMwServices().
         *
         * @since 1.21
         */
        protected function mergeMwGlobalArrayValue( $name, $values ) {
                if ( !isset( $GLOBALS[$name] ) ) {
                        $merged = $values;
                } else {
                        if ( !is_array( $GLOBALS[$name] ) ) {
                                throw new MWException( "MW global $name is not an array." );
                        }

                        // NOTE: do not use array_merge, it screws up for numeric keys.
                        $merged = $GLOBALS[$name];
                        foreach ( $values as $k => $v ) {
                                $merged[$k] = $v;
                        }
                }

                $this->setMwGlobals( $name, $merged );
        }

        /**
         * Stashes the global instance of MediaWikiServices, and installs a new one,
         * allowing test cases to override settings and services.
         * The previous instance of MediaWikiServices will be restored on tearDown.
         *
         * @since 1.27
         *
         * @param Config|null $configOverrides Configuration overrides for the new MediaWikiServices
         *        instance.
         * @param callable[] $services An associative array of services to re-define. Keys are service
         *        names, values are callables.
         *
         * @return MediaWikiServices
         * @throws MWException
         */
        protected static function overrideMwServices(
                Config $configOverrides = null, array $services = []
        ) {
                if ( !$configOverrides ) {
                        $configOverrides = new HashConfig();
                }

                $oldInstance = MediaWikiServices::getInstance();
                $oldConfigFactory = $oldInstance->getConfigFactory();
                $oldLoadBalancerFactory = $oldInstance->getDBLoadBalancerFactory();

                $testConfig = self::makeTestConfig( null, $configOverrides );
                $newInstance = new MediaWikiServices( $testConfig );

                // Load the default wiring from the specified files.
                // NOTE: this logic mirrors the logic in MediaWikiServices::newInstance.
                $wiringFiles = $testConfig->get( 'ServiceWiringFiles' );
                $newInstance->loadWiringFiles( $wiringFiles );

                // Provide a traditional hook point to allow extensions to configure services.
                Hooks::run( 'MediaWikiServices', [ $newInstance ] );

                foreach ( $services as $name => $callback ) {
                        $newInstance->redefineService( $name, $callback );
                }

                self::installTestServices(
                        $oldConfigFactory,
                        $oldLoadBalancerFactory,
                        $newInstance
                );
                MediaWikiServices::forceGlobalInstance( $newInstance );

                return $newInstance;
        }

        /**
         * @since 1.27
         * @param string|Language $lang
         */
        public function setUserLang( $lang ) {
                RequestContext::getMain()->setLanguage( $lang );
                $this->setMwGlobals( 'wgLang', RequestContext::getMain()->getLanguage() );
        }

        /**
         * @since 1.27
         * @param string|Language $lang
         */
        public function setContentLang( $lang ) {
                if ( $lang instanceof Language ) {
                        $langCode = $lang->getCode();
                        $langObj = $lang;
                } else {
                        $langCode = $lang;
                        $langObj = Language::factory( $langCode );
                }
                $this->setMwGlobals( 'wgLanguageCode', $langCode );
                $this->setService( 'ContentLanguage', $langObj );
        }

        /**
         * Alters $wgGroupPermissions for the duration of the test.  Can be called
         * with an array, like
         *   [ '*' => [ 'read' => false ], 'user' => [ 'read' => false ] ]
         * or three values to set a single permission, like
         *   $this->setGroupPermissions( '*', 'read', false );
         *
         * @since 1.31
         * @param array|string $newPerms Either an array of permissions to change,
         *   in which case the next two parameters are ignored; or a single string
         *   identifying a group, to use with the next two parameters.
         * @param string|null $newKey
         * @param mixed|null $newValue
         */
        public function setGroupPermissions( $newPerms, $newKey = null, $newValue = null ) {
                global $wgGroupPermissions;

                $this->stashMwGlobals( 'wgGroupPermissions' );

                if ( is_string( $newPerms ) ) {
                        $newPerms = [ $newPerms => [ $newKey => $newValue ] ];
                }

                foreach ( $newPerms as $group => $permissions ) {
                        foreach ( $permissions as $key => $value ) {
                                $wgGroupPermissions[$group][$key] = $value;
                        }
                }
        }

        /**
         * Sets the logger for a specified channel, for the duration of the test.
         * @since 1.27
         * @param string $channel
         * @param LoggerInterface $logger
         */
        protected function setLogger( $channel, LoggerInterface $logger ) {
                // TODO: Once loggers are managed by MediaWikiServices, use
                //       overrideMwServices() to set loggers.

                $provider = LoggerFactory::getProvider();
                $wrappedProvider = TestingAccessWrapper::newFromObject( $provider );
                $singletons = $wrappedProvider->singletons;
                if ( $provider instanceof MonologSpi ) {
                        if ( !isset( $this->loggers[$channel] ) ) {
                                $this->loggers[$channel] = $singletons['loggers'][$channel] ?? null;
                        }
                        $singletons['loggers'][$channel] = $logger;
                } elseif ( $provider instanceof LegacySpi ) {
                        if ( !isset( $this->loggers[$channel] ) ) {
                                $this->loggers[$channel] = $singletons[$channel] ?? null;
                        }
                        $singletons[$channel] = $logger;
                } else {
                        throw new LogicException( __METHOD__ . ': setting a logger for ' . get_class( $provider )
                                . ' is not implemented' );
                }
                $wrappedProvider->singletons = $singletons;
        }

        /**
         * Restores loggers replaced by setLogger().
         * @since 1.27
         */
        private function restoreLoggers() {
                $provider = LoggerFactory::getProvider();
                $wrappedProvider = TestingAccessWrapper::newFromObject( $provider );
                $singletons = $wrappedProvider->singletons;
                foreach ( $this->loggers as $channel => $logger ) {
                        if ( $provider instanceof MonologSpi ) {
                                if ( $logger === null ) {
                                        unset( $singletons['loggers'][$channel] );
                                } else {
                                        $singletons['loggers'][$channel] = $logger;
                                }
                        } elseif ( $provider instanceof LegacySpi ) {
                                if ( $logger === null ) {
                                        unset( $singletons[$channel] );
                                } else {
                                        $singletons[$channel] = $logger;
                                }
                        }
                }
                $wrappedProvider->singletons = $singletons;
                $this->loggers = [];
        }

        /**
         * @return string
         * @since 1.18
         */
        public function dbPrefix() {
                return self::getTestPrefixFor( $this->db );
        }

        /**
         * @param IDatabase $db
         * @return string
         * @since 1.32
         */
        public static function getTestPrefixFor( IDatabase $db ) {
                return $db->getType() == 'oracle' ? self::ORA_DB_PREFIX : self::DB_PREFIX;
        }

        /**
         * @return bool
         * @since 1.18
         */
        public function needsDB() {
                // If the test says it uses database tables, it needs the database
                if ( $this->tablesUsed ) {
                        return true;
                }

                // If the test class says it belongs to the Database group, it needs the database.
                // NOTE: This ONLY checks for the group in the class level doc comment.
                $rc = new ReflectionClass( $this );
                if ( preg_match( '/@group +Database/im', $rc->getDocComment() ) ) {
                        return true;
                }

                return false;
        }

        /**
         * Insert a new page.
         *
         * Should be called from addDBData().
         *
         * @since 1.25 ($namespace in 1.28)
         * @param string|Title $pageName Page name or title
         * @param string $text Page's content
         * @param int|null $namespace Namespace id (name cannot already contain namespace)
         * @param User|null $user If null, static::getTestSysop()->getUser() is used.
         * @return array Title object and page id
         */
        protected function insertPage(
                $pageName,
                $text = 'Sample page for unit test.',
                $namespace = null,
                User $user = null
        ) {
                if ( is_string( $pageName ) ) {
                        $title = Title::newFromText( $pageName, $namespace );
                } else {
                        $title = $pageName;
                }

                if ( !$user ) {
                        $user = static::getTestSysop()->getUser();
                }
                $comment = __METHOD__ . ': Sample page for unit test.';

                $page = WikiPage::factory( $title );
                $page->doEditContent( ContentHandler::makeContent( $text, $title ), $comment, 0, false, $user );

                return [
                        'title' => $title,
                        'id' => $page->getId(),
                ];
        }

        /**
         * Stub. If a test suite needs to add additional data to the database, it should
         * implement this method and do so. This method is called once per test suite
         * (i.e. once per class).
         *
         * Note data added by this method may be removed by resetDB() depending on
         * the contents of $tablesUsed.
         *
         * To add additional data between test function runs, override prepareDB().
         *
         * @see addDBData()
         * @see resetDB()
         *
         * @since 1.27
         */
        public function addDBDataOnce() {
        }

        /**
         * Stub. Subclasses may override this to prepare the database.
         * Called before every test run (test function or data set).
         *
         * @see addDBDataOnce()
         * @see resetDB()
         *
         * @since 1.18
         */
        public function addDBData() {
        }

        /**
         * @since 1.32
         */
        protected function addCoreDBData() {
                if ( $this->db->getType() == 'oracle' ) {
                        # Insert 0 user to prevent FK violations
                        # Anonymous user
                        if ( !$this->db->selectField( 'user', '1', [ 'user_id' => 0 ] ) ) {
                                $this->db->insert( 'user', [
                                        'user_id' => 0,
                                        'user_name' => 'Anonymous' ], __METHOD__, [ 'IGNORE' ] );
                        }

                        # Insert 0 page to prevent FK violations
                        # Blank page
                        if ( !$this->db->selectField( 'page', '1', [ 'page_id' => 0 ] ) ) {
                                $this->db->insert( 'page', [
                                        'page_id' => 0,
                                        'page_namespace' => 0,
                                        'page_title' => ' ',
                                        'page_restrictions' => null,
                                        'page_is_redirect' => 0,
                                        'page_is_new' => 0,
                                        'page_random' => 0,
                                        'page_touched' => $this->db->timestamp(),
                                        'page_latest' => 0,
                                        'page_len' => 0 ], __METHOD__, [ 'IGNORE' ] );
                        }
                }

                SiteStatsInit::doPlaceholderInit();

                User::resetIdByNameCache();

                // Make sysop user
                $user = static::getTestSysop()->getUser();

                // Make 1 page with 1 revision
                $page = WikiPage::factory( Title::newFromText( 'UTPage' ) );
                if ( $page->getId() == 0 ) {
                        $page->doEditContent(
                                new WikitextContent( 'UTContent' ),
                                'UTPageSummary',
                                EDIT_NEW | EDIT_SUPPRESS_RC,
                                false,
                                $user
                        );
                        // an edit always attempt to purge backlink links such as history
                        // pages. That is unnecessary.
                        JobQueueGroup::singleton()->get( 'htmlCacheUpdate' )->delete();
                        // WikiPages::doEditUpdates randomly adds RC purges
                        JobQueueGroup::singleton()->get( 'recentChangesUpdate' )->delete();

                        // doEditContent() probably started the session via
                        // User::loadFromSession(). Close it now.
                        if ( session_id() !== '' ) {
                                session_write_close();
                                session_id( '' );
                        }
                }
        }

        /**
         * Restores MediaWiki to using the table set (table prefix) it was using before
         * setupTestDB() was called. Useful if we need to perform database operations
         * after the test run has finished (such as saving logs or profiling info).
         *
         * This is called by phpunit/bootstrap.php after the last test.
         *
         * @since 1.21
         */
        public static function teardownTestDB() {
                global $wgJobClasses;

                if ( !self::$dbSetup ) {
                        return;
                }

                Hooks::run( 'UnitTestsBeforeDatabaseTeardown' );

                foreach ( $wgJobClasses as $type => $class ) {
                        // Delete any jobs under the clone DB (or old prefix in other stores)
                        JobQueueGroup::singleton()->get( $type )->delete();
                }

                CloneDatabase::changePrefix( self::$oldTablePrefix );

                self::$oldTablePrefix = false;
                self::$dbSetup = false;
        }

        /**
         * Prepares the given database connection for usage in the context of usage tests.
         * This sets up clones database tables and changes the table prefix as appropriate.
         * If the database connection already has cloned tables, calling this method has no
         * effect. The tables are not re-cloned or reset in that case.
         *
         * @param IMaintainableDatabase $db
         */
        protected function prepareConnectionForTesting( IMaintainableDatabase $db ) {
                if ( !self::$dbSetup ) {
                        throw new LogicException(
                                'Cannot use prepareConnectionForTesting()'
                                . ' if the test case is not defined to use the database!'
                        );
                }

                if ( isset( $db->_originalTablePrefix ) ) {
                        // The DB connection was already prepared for testing.
                        return;
                }

                $testPrefix = self::getTestPrefixFor( $db );
                $oldPrefix = $db->tablePrefix();

                $tablesCloned = self::listTables( $db );

                if ( $oldPrefix === $testPrefix ) {
                        // The database connection already has the test prefix, but presumably not
                        // the cloned tables. This is the typical case, since the LBFactory will
                        // have the prefix set during testing, but LoadBalancers will still return
                        // connections that don't have the cloned table structure.
                        $oldPrefix = self::$oldTablePrefix;
                }

                $dbClone = new CloneDatabase( $db, $tablesCloned, $testPrefix, $oldPrefix );
                $dbClone->useTemporaryTables( self::$useTemporaryTables );

                $db->_originalTablePrefix = $oldPrefix;

                if ( ( $db->getType() == 'oracle' || !self::$useTemporaryTables ) && self::$reuseDB ) {
                        throw new LogicException( 'Cannot clone database tables' );
                } else {
                        $dbClone->cloneTableStructure();
                }
        }

        /**
         * Setups a database with cloned tables using the given prefix.
         *
         * If reuseDB is true and certain conditions apply, it will just change the prefix.
         * Otherwise, it will clone the tables and change the prefix.
         *
         * @param IMaintainableDatabase $db Database to use
         * @param string|null $prefix Prefix to use for test tables. If not given, the prefix is determined
         *        automatically for $db.
         * @return bool True if tables were cloned, false if only the prefix was changed
         */
        protected static function setupDatabaseWithTestPrefix(
                IMaintainableDatabase $db,
                $prefix = null
        ) {
                if ( $prefix === null ) {
                        $prefix = self::getTestPrefixFor( $db );
                }

                if ( ( $db->getType() == 'oracle' || !self::$useTemporaryTables ) && self::$reuseDB ) {
                        $db->tablePrefix( $prefix );
                        return false;
                }

                if ( !isset( $db->_originalTablePrefix ) ) {
                        $oldPrefix = $db->tablePrefix();

                        if ( $oldPrefix === $prefix ) {
                                // table already has the correct prefix, but presumably no cloned tables
                                $oldPrefix = self::$oldTablePrefix;
                        }

                        $db->tablePrefix( $oldPrefix );
                        $tablesCloned = self::listTables( $db );
                        $dbClone = new CloneDatabase( $db, $tablesCloned, $prefix, $oldPrefix );
                        $dbClone->useTemporaryTables( self::$useTemporaryTables );

                        $dbClone->cloneTableStructure();

                        $db->tablePrefix( $prefix );
                        $db->_originalTablePrefix = $oldPrefix;
                }

                return true;
        }

        /**
         * Set up all test DBs
         */
        public function setupAllTestDBs() {
                global $wgDBprefix;

                self::$oldTablePrefix = $wgDBprefix;

                $testPrefix = $this->dbPrefix();

                // switch to a temporary clone of the database
                self::setupTestDB( $this->db, $testPrefix );

                if ( self::isUsingExternalStoreDB() ) {
                        self::setupExternalStoreTestDBs( $testPrefix );
                }

                // NOTE: Change the prefix in the LBFactory and $wgDBprefix, to prevent
                // *any* database connections to operate on live data.
                CloneDatabase::changePrefix( $testPrefix );
        }

        /**
         * Creates an empty skeleton of the wiki database by cloning its structure
         * to equivalent tables using the given $prefix. Then sets MediaWiki to
         * use the new set of tables (aka schema) instead of the original set.
         *
         * This is used to generate a dummy table set, typically consisting of temporary
         * tables, that will be used by tests instead of the original wiki database tables.
         *
         * @since 1.21
         *
         * @note the original table prefix is stored in self::$oldTablePrefix. This is used
         * by teardownTestDB() to return the wiki to using the original table set.
         *
         * @note this method only works when first called. Subsequent calls have no effect,
         * even if using different parameters.
         *
         * @param Database $db The database connection
         * @param string $prefix The prefix to use for the new table set (aka schema).
         *
         * @throws MWException If the database table prefix is already $prefix
         */
        public static function setupTestDB( Database $db, $prefix ) {
                if ( self::$dbSetup ) {
                        return;
                }

                if ( $db->tablePrefix() === $prefix ) {
                        throw new MWException(
                                'Cannot run unit tests, the database prefix is already "' . $prefix . '"' );
                }

                // TODO: the below should be re-written as soon as LBFactory, LoadBalancer,
                // and Database no longer use global state.

                self::$dbSetup = true;

                if ( !self::setupDatabaseWithTestPrefix( $db, $prefix ) ) {
                        return;
                }

                // Assuming this isn't needed for External Store database, and not sure if the procedure
                // would be available there.
                if ( $db->getType() == 'oracle' ) {
                        $db->query( 'BEGIN FILL_WIKI_INFO; END;' );
                }

                Hooks::run( 'UnitTestsAfterDatabaseSetup', [ $db, $prefix ] );
        }

        /**
         * Clones the External Store database(s) for testing
         *
         * @param string|null $testPrefix Prefix for test tables. Will be determined automatically
         *        if not given.
         */
        protected static function setupExternalStoreTestDBs( $testPrefix = null ) {
                $connections = self::getExternalStoreDatabaseConnections();
                foreach ( $connections as $dbw ) {
                        self::setupDatabaseWithTestPrefix( $dbw, $testPrefix );
                }
        }

        /**
         * Gets master database connections for all of the ExternalStoreDB
         * stores configured in $wgDefaultExternalStore.
         *
         * @return Database[] Array of Database master connections
         */
        protected static function getExternalStoreDatabaseConnections() {
                global $wgDefaultExternalStore;

                /** @var ExternalStoreDB $externalStoreDB */
                $externalStoreDB = ExternalStore::getStoreObject( 'DB' );
                $defaultArray = (array)$wgDefaultExternalStore;
                $dbws = [];
                foreach ( $defaultArray as $url ) {
                        if ( strpos( $url, 'DB://' ) === 0 ) {
                                list( $proto, $cluster ) = explode( '://', $url, 2 );
                                // Avoid getMaster() because setupDatabaseWithTestPrefix()
                                // requires Database instead of plain DBConnRef/IDatabase
                                $dbws[] = $externalStoreDB->getMaster( $cluster );
                        }
                }

                return $dbws;
        }

        /**
         * Check whether ExternalStoreDB is being used
         *
         * @return bool True if it's being used
         */
        protected static function isUsingExternalStoreDB() {
                global $wgDefaultExternalStore;
                if ( !$wgDefaultExternalStore ) {
                        return false;
                }

                $defaultArray = (array)$wgDefaultExternalStore;
                foreach ( $defaultArray as $url ) {
                        if ( strpos( $url, 'DB://' ) === 0 ) {
                                return true;
                        }
                }

                return false;
        }

        /**
         * @throws LogicException if the given database connection is not a set up to use
         * mock tables.
         *
         * @since 1.31 this is no longer private.
         */
        protected function ensureMockDatabaseConnection( IDatabase $db ) {
                if ( $db->tablePrefix() !== $this->dbPrefix() ) {
                        throw new LogicException(
                                'Trying to delete mock tables, but table prefix does not indicate a mock database.'
                        );
                }
        }

        private static $schemaOverrideDefaults = [
                'scripts' => [],
                'create' => [],
                'drop' => [],
                'alter' => [],
        ];

        /**
         * Stub. If a test suite needs to test against a specific database schema, it should
         * override this method and return the appropriate information from it.
         *
         * @param IMaintainableDatabase $db The DB connection to use for the mock schema.
         *        May be used to check the current state of the schema, to determine what
         *        overrides are needed.
         *
         * @return array An associative array with the following fields:
         *  - 'scripts': any SQL scripts to run. If empty or not present, schema overrides are skipped.
         * - 'create': A list of tables created (may or may not exist in the original schema).
         * - 'drop': A list of tables dropped (expected to be present in the original schema).
         * - 'alter': A list of tables altered (expected to be present in the original schema).
         */
        protected function getSchemaOverrides( IMaintainableDatabase $db ) {
                return [];
        }

        /**
         * Undoes the specified schema overrides..
         * Called once per test class, just before addDataOnce().
         *
         * @param IMaintainableDatabase $db
         * @param array $oldOverrides
         */
        private function undoSchemaOverrides( IMaintainableDatabase $db, $oldOverrides ) {
                $this->ensureMockDatabaseConnection( $db );

                $oldOverrides = $oldOverrides + self::$schemaOverrideDefaults;
                $originalTables = $this->listOriginalTables( $db, 'unprefixed' );

                // Drop tables that need to be restored or removed.
                $tablesToDrop = array_merge( $oldOverrides['create'], $oldOverrides['alter'] );

                // Restore tables that have been dropped or created or altered,
                // if they exist in the original schema.
                $tablesToRestore = array_merge( $tablesToDrop, $oldOverrides['drop'] );
                $tablesToRestore = array_intersect( $originalTables, $tablesToRestore );

                if ( $tablesToDrop ) {
                        $this->dropMockTables( $db, $tablesToDrop );
                }

                if ( $tablesToRestore ) {
                        $this->recloneMockTables( $db, $tablesToRestore );
                }
        }

        /**
         * Applies the schema overrides returned by getSchemaOverrides(),
         * after undoing any previously applied schema overrides.
         * Called once per test class, just before addDataOnce().
         */
        private function setUpSchema( IMaintainableDatabase $db ) {
                // Undo any active overrides.
                $oldOverrides = $db->_schemaOverrides ?? self::$schemaOverrideDefaults;

                if ( $oldOverrides['alter'] || $oldOverrides['create'] || $oldOverrides['drop'] ) {
                        $this->undoSchemaOverrides( $db, $oldOverrides );
                }

                // Determine new overrides.
                $overrides = $this->getSchemaOverrides( $db ) + self::$schemaOverrideDefaults;

                $extraKeys = array_diff(
                        array_keys( $overrides ),
                        array_keys( self::$schemaOverrideDefaults )
                );

                if ( $extraKeys ) {
                        throw new InvalidArgumentException(
                                'Schema override contains extra keys: ' . var_export( $extraKeys, true )
                        );
                }

                if ( !$overrides['scripts'] ) {
                        // no scripts to run
                        return;
                }

                if ( !$overrides['create'] && !$overrides['drop'] && !$overrides['alter'] ) {
                        throw new InvalidArgumentException(
                                'Schema override scripts given, but no tables are declared to be '
                                . 'created, dropped or altered.'
                        );
                }

                $this->ensureMockDatabaseConnection( $db );

                // Drop the tables that will be created by the schema scripts.
                $originalTables = $this->listOriginalTables( $db, 'unprefixed' );
                $tablesToDrop = array_intersect( $originalTables, $overrides['create'] );

                if ( $tablesToDrop ) {
                        $this->dropMockTables( $db, $tablesToDrop );
                }

                // Run schema override scripts.
                foreach ( $overrides['scripts'] as $script ) {
                        $db->sourceFile(
                                $script,
                                null,
                                null,
                                __METHOD__,
                                function ( $cmd ) {
                                        return $this->mungeSchemaUpdateQuery( $cmd );
                                }
                        );
                }

                $db->_schemaOverrides = $overrides;
        }

        private function mungeSchemaUpdateQuery( $cmd ) {
                return self::$useTemporaryTables
                        ? preg_replace( '/\bCREATE\s+TABLE\b/i', 'CREATE TEMPORARY TABLE', $cmd )
                        : $cmd;
        }

        /**
         * Drops the given mock tables.
         *
         * @param IMaintainableDatabase $db
         * @param array $tables
         */
        private function dropMockTables( IMaintainableDatabase $db, array $tables ) {
                $this->ensureMockDatabaseConnection( $db );

                foreach ( $tables as $tbl ) {
                        $tbl = $db->tableName( $tbl );
                        $db->query( "DROP TABLE IF EXISTS $tbl", __METHOD__ );

                        if ( $tbl === 'page' ) {
                                // Forget about the pages since they don't
                                // exist in the DB.
                                MediaWikiServices::getInstance()->getLinkCache()->clear();
                        }
                }
        }

        /**
         * Lists all tables in the live database schema.
         *
         * @param IMaintainableDatabase $db
         * @param string $prefix Either 'prefixed' or 'unprefixed'
         * @return array
         */
        private function listOriginalTables( IMaintainableDatabase $db, $prefix = 'prefixed' ) {
                if ( !isset( $db->_originalTablePrefix ) ) {
                        throw new LogicException( 'No original table prefix know, cannot list tables!' );
                }

                $originalTables = $db->listTables( $db->_originalTablePrefix, __METHOD__ );
                if ( $prefix === 'unprefixed' ) {
                        $originalPrefixRegex = '/^' . preg_quote( $db->_originalTablePrefix ) . '/';
                        $originalTables = array_map(
                                function ( $pt ) use ( $originalPrefixRegex ) {
                                        return preg_replace( $originalPrefixRegex, '', $pt );
                                },
                                $originalTables
                        );
                }

                return $originalTables;
        }

        /**
         * Re-clones the given mock tables to restore them based on the live database schema.
         * The tables listed in $tables are expected to currently not exist, so dropMockTables()
         * should be called first.
         *
         * @param IMaintainableDatabase $db
         * @param array $tables
         */
        private function recloneMockTables( IMaintainableDatabase $db, array $tables ) {
                $this->ensureMockDatabaseConnection( $db );

                if ( !isset( $db->_originalTablePrefix ) ) {
                        throw new LogicException( 'No original table prefix know, cannot restore tables!' );
                }

                $originalTables = $this->listOriginalTables( $db, 'unprefixed' );
                $tables = array_intersect( $tables, $originalTables );

                $dbClone = new CloneDatabase( $db, $tables, $db->tablePrefix(), $db->_originalTablePrefix );
                $dbClone->useTemporaryTables( self::$useTemporaryTables );

                $dbClone->cloneTableStructure();
        }

        /**
         * Empty all tables so they can be repopulated for tests
         *
         * @param Database $db|null Database to reset
         * @param array $tablesUsed Tables to reset
         */
        private function resetDB( $db, $tablesUsed ) {
                if ( $db ) {
                        // NOTE: Do not reset the slot_roles and content_models tables, but let them
                        // leak across tests. Resetting them would require to reset all NamedTableStore
                        // instances for these tables, of which there may be several beyond the ones
                        // known to MediaWikiServices. See T202641.
                        $userTables = [ 'user', 'user_groups', 'user_properties', 'actor' ];
                        $pageTables = [
                                'page', 'revision', 'ip_changes', 'revision_comment_temp', 'comment', 'archive',
                                'revision_actor_temp', 'slots', 'content',
                        ];
                        $coreDBDataTables = array_merge( $userTables, $pageTables );

                        // If any of the user or page tables were marked as used, we should clear all of them.
                        if ( array_intersect( $tablesUsed, $userTables ) ) {
                                $tablesUsed = array_unique( array_merge( $tablesUsed, $userTables ) );
                                TestUserRegistry::clear();
                        }
                        if ( array_intersect( $tablesUsed, $pageTables ) ) {
                                $tablesUsed = array_unique( array_merge( $tablesUsed, $pageTables ) );
                        }

                        // Postgres, Oracle, and MSSQL all use mwuser/pagecontent
                        // instead of user/text. But Postgres does not remap the
                        // table name in tableExists(), so we mark the real table
                        // names as being used.
                        if ( $db->getType() === 'postgres' ) {
                                if ( in_array( 'user', $tablesUsed ) ) {
                                        $tablesUsed[] = 'mwuser';
                                }
                                if ( in_array( 'text', $tablesUsed ) ) {
                                        $tablesUsed[] = 'pagecontent';
                                }
                        }

                        foreach ( $tablesUsed as $tbl ) {
                                $this->truncateTable( $tbl, $db );
                        }

                        if ( array_intersect( $tablesUsed, $coreDBDataTables ) ) {
                                // Re-add core DB data that was deleted
                                $this->addCoreDBData();
                        }
                }
        }

        /**
         * Empties the given table and resets any auto-increment counters.
         * Will also purge caches associated with some well known tables.
         * If the table is not know, this method just returns.
         *
         * @param string $tableName
         * @param IDatabase|null $db
         */
        protected function truncateTable( $tableName, IDatabase $db = null ) {
                if ( !$db ) {
                        $db = $this->db;
                }

                if ( !$db->tableExists( $tableName ) ) {
                        return;
                }

                $truncate = in_array( $db->getType(), [ 'oracle', 'mysql' ] );

                if ( $truncate ) {
                        $db->query( 'TRUNCATE TABLE ' . $db->tableName( $tableName ), __METHOD__ );
                } else {
                        $db->delete( $tableName, '*', __METHOD__ );
                }

                if ( in_array( $db->getType(), [ 'postgres', 'sqlite' ], true ) ) {
                        // Reset the table's sequence too.
                        $db->resetSequenceForTable( $tableName, __METHOD__ );
                }

                if ( $tableName === 'interwiki' ) {
                        if ( !$this->interwikiTable ) {
                                // @todo We should probably throw here, but this causes test failures that I
                                // can't figure out, so for now we silently continue.
                                return;
                        }
                        $db->insert(
                                'interwiki',
                                array_values( array_map( 'get_object_vars', iterator_to_array( $this->interwikiTable ) ) ),
                                __METHOD__
                        );
                }

                if ( $tableName === 'page' ) {
                        // Forget about the pages since they don't
                        // exist in the DB.
                        MediaWikiServices::getInstance()->getLinkCache()->clear();
                }
        }

        private static function unprefixTable( &$tableName, $ind, $prefix ) {
                $tableName = substr( $tableName, strlen( $prefix ) );
        }

        private static function isNotUnittest( $table ) {
                return strpos( $table, self::DB_PREFIX ) !== 0;
        }

        /**
         * @since 1.18
         *
         * @param IMaintainableDatabase $db
         *
         * @return array
         */
        public static function listTables( IMaintainableDatabase $db ) {
                $prefix = $db->tablePrefix();
                $tables = $db->listTables( $prefix, __METHOD__ );

                if ( $db->getType() === 'mysql' ) {
                        static $viewListCache = null;
                        if ( $viewListCache === null ) {
                                $viewListCache = $db->listViews( null, __METHOD__ );
                        }
                        // T45571: cannot clone VIEWs under MySQL
                        $tables = array_diff( $tables, $viewListCache );
                }
                array_walk( $tables, [ __CLASS__, 'unprefixTable' ], $prefix );

                // Don't duplicate test tables from the previous fataled run
                $tables = array_filter( $tables, [ __CLASS__, 'isNotUnittest' ] );

                if ( $db->getType() == 'sqlite' ) {
                        $tables = array_flip( $tables );
                        // these are subtables of searchindex and don't need to be duped/dropped separately
                        unset( $tables['searchindex_content'] );
                        unset( $tables['searchindex_segdir'] );
                        unset( $tables['searchindex_segments'] );
                        $tables = array_flip( $tables );
                }

                return $tables;
        }

        /**
         * Copy test data from one database connection to another.
         *
         * This should only be used for small data sets.
         *
         * @param IDatabase $source
         * @param IDatabase $target
         */
        public function copyTestData( IDatabase $source, IDatabase $target ) {
                $tables = self::listOriginalTables( $source, 'unprefixed' );

                foreach ( $tables as $table ) {
                        $res = $source->select( $table, '*', [], __METHOD__ );
                        $allRows = [];

                        foreach ( $res as $row ) {
                                $allRows[] = (array)$row;
                        }

                        $target->insert( $table, $allRows, __METHOD__, [ 'IGNORE' ] );
                }
        }

        /**
         * @throws MWException
         * @since 1.18
         */
        protected function checkDbIsSupported() {
                if ( !in_array( $this->db->getType(), $this->supportedDBs ) ) {
                        throw new MWException( $this->db->getType() . " is not currently supported for unit testing." );
                }
        }

        /**
         * @since 1.18
         * @param string $offset
         * @return mixed
         */
        public function getCliArg( $offset ) {
                if ( isset( PHPUnitMaintClass::$additionalOptions[$offset] ) ) {
                        return PHPUnitMaintClass::$additionalOptions[$offset];
                }

                return null;
        }

        /**
         * @since 1.18
         * @param string $offset
         * @param mixed $value
         */
        public function setCliArg( $offset, $value ) {
                PHPUnitMaintClass::$additionalOptions[$offset] = $value;
        }

        /**
         * Don't throw a warning if $function is deprecated and called later
         *
         * @since 1.19
         *
         * @param string $function
         */
        public function hideDeprecated( $function ) {
                Wikimedia\suppressWarnings();
                wfDeprecated( $function );
                Wikimedia\restoreWarnings();
        }

        /**
         * Asserts that the given database query yields the rows given by $expectedRows.
         * The expected rows should be given as indexed (not associative) arrays, with
         * the values given in the order of the columns in the $fields parameter.
         * Note that the rows are sorted by the columns given in $fields.
         *
         * @since 1.20
         *
         * @param string|array $table The table(s) to query
         * @param string|array $fields The columns to include in the result (and to sort by)
         * @param string|array $condition "where" condition(s)
         * @param array $expectedRows An array of arrays giving the expected rows.
         * @param array $options Options for the query
         * @param array $join_conds Join conditions for the query
         *
         * @throws MWException If this test cases's needsDB() method doesn't return true.
         *         Test cases can use "@group Database" to enable database test support,
         *         or list the tables under testing in $this->tablesUsed, or override the
         *         needsDB() method.
         */
        protected function assertSelect(
                $table, $fields, $condition, array $expectedRows, array $options = [], array $join_conds = []
        ) {
                if ( !$this->needsDB() ) {
                        throw new MWException( 'When testing database state, the test cases\'s needDB()' .
                                ' method should return true. Use @group Database or $this->tablesUsed.' );
                }

                $db = wfGetDB( DB_REPLICA );

                $res = $db->select(
                        $table,
                        $fields,
                        $condition,
                        wfGetCaller(),
                        $options + [ 'ORDER BY' => $fields ],
                        $join_conds
                );
                $this->assertNotEmpty( $res, "query failed: " . $db->lastError() );

                $i = 0;

                foreach ( $expectedRows as $expected ) {
                        $r = $res->fetchRow();
                        self::stripStringKeys( $r );

                        $i += 1;
                        $this->assertNotEmpty( $r, "row #$i missing" );

                        $this->assertEquals( $expected, $r, "row #$i mismatches" );
                }

                $r = $res->fetchRow();
                self::stripStringKeys( $r );

                $this->assertFalse( $r, "found extra row (after #$i)" );
        }

        /**
         * Utility method taking an array of elements and wrapping
         * each element in its own array. Useful for data providers
         * that only return a single argument.
         *
         * @since 1.20
         *
         * @param array $elements
         *
         * @return array
         */
        protected function arrayWrap( array $elements ) {
                return array_map(
                        function ( $element ) {
                                return [ $element ];
                        },
                        $elements
                );
        }

        /**
         * Assert that two arrays are equal. By default this means that both arrays need to hold
         * the same set of values. Using additional arguments, order and associated key can also
         * be set as relevant.
         *
         * @since 1.20
         *
         * @param array $expected
         * @param array $actual
         * @param bool $ordered If the order of the values should match
         * @param bool $named If the keys should match
         */
        protected function assertArrayEquals( array $expected, array $actual,
                $ordered = false, $named = false
        ) {
                if ( !$ordered ) {
                        $this->objectAssociativeSort( $expected );
                        $this->objectAssociativeSort( $actual );
                }

                if ( !$named ) {
                        $expected = array_values( $expected );
                        $actual = array_values( $actual );
                }

                call_user_func_array(
                        [ $this, 'assertEquals' ],
                        array_merge( [ $expected, $actual ], array_slice( func_get_args(), 4 ) )
                );
        }

        /**
         * Put each HTML element on its own line and then equals() the results
         *
         * Use for nicely formatting of PHPUnit diff output when comparing very
         * simple HTML
         *
         * @since 1.20
         *
         * @param string $expected HTML on oneline
         * @param string $actual HTML on oneline
         * @param string $msg Optional message
         */
        protected function assertHTMLEquals( $expected, $actual, $msg = '' ) {
                $expected = str_replace( '>', ">\n", $expected );
                $actual = str_replace( '>', ">\n", $actual );

                $this->assertEquals( $expected, $actual, $msg );
        }

        /**
         * Does an associative sort that works for objects.
         *
         * @since 1.20
         *
         * @param array &$array
         */
        protected function objectAssociativeSort( array &$array ) {
                uasort(
                        $array,
                        function ( $a, $b ) {
                                return serialize( $a ) <=> serialize( $b );
                        }
                );
        }

        /**
         * Utility function for eliminating all string keys from an array.
         * Useful to turn a database result row as returned by fetchRow() into
         * a pure indexed array.
         *
         * @since 1.20
         *
         * @param mixed &$r The array to remove string keys from.
         */
        protected static function stripStringKeys( &$r ) {
                if ( !is_array( $r ) ) {
                        return;
                }

                foreach ( $r as $k => $v ) {
                        if ( is_string( $k ) ) {
                                unset( $r[$k] );
                        }
                }
        }

        /**
         * Asserts that the provided variable is of the specified
         * internal type or equals the $value argument. This is useful
         * for testing return types of functions that return a certain
         * type or *value* when not set or on error.
         *
         * @since 1.20
         *
         * @param string $type
         * @param mixed $actual
         * @param mixed $value
         * @param string $message
         */
        protected function assertTypeOrValue( $type, $actual, $value = false, $message = '' ) {
                if ( $actual === $value ) {
                        $this->assertTrue( true, $message );
                } else {
                        $this->assertType( $type, $actual, $message );
                }
        }

        /**
         * Asserts the type of the provided value. This can be either
         * in internal type such as boolean or integer, or a class or
         * interface the value extends or implements.
         *
         * @since 1.20
         *
         * @param string $type
         * @param mixed $actual
         * @param string $message
         */
        protected function assertType( $type, $actual, $message = '' ) {
                if ( class_exists( $type ) || interface_exists( $type ) ) {
                        $this->assertInstanceOf( $type, $actual, $message );
                } else {
                        $this->assertInternalType( $type, $actual, $message );
                }
        }

        /**
         * Returns true if the given namespace defaults to Wikitext
         * according to $wgNamespaceContentModels
         *
         * @param int $ns The namespace ID to check
         *
         * @return bool
         * @since 1.21
         */
        protected function isWikitextNS( $ns ) {
                global $wgNamespaceContentModels;

                if ( isset( $wgNamespaceContentModels[$ns] ) ) {
                        return $wgNamespaceContentModels[$ns] === CONTENT_MODEL_WIKITEXT;
                }

                return true;
        }

        /**
         * Returns the ID of a namespace that defaults to Wikitext.
         *
         * @throws MWException If there is none.
         * @return int The ID of the wikitext Namespace
         * @since 1.21
         */
        protected function getDefaultWikitextNS() {
                global $wgNamespaceContentModels;

                static $wikitextNS = null; // this is not going to change
                if ( $wikitextNS !== null ) {
                        return $wikitextNS;
                }

                // quickly short out on most common case:
                if ( !isset( $wgNamespaceContentModels[NS_MAIN] ) ) {
                        return NS_MAIN;
                }

                // NOTE: prefer content namespaces
                $namespaces = array_unique( array_merge(
                        MWNamespace::getContentNamespaces(),
                        [ NS_MAIN, NS_HELP, NS_PROJECT ], // prefer these
                        MWNamespace::getValidNamespaces()
                ) );

                $namespaces = array_diff( $namespaces, [
                        NS_FILE, NS_CATEGORY, NS_MEDIAWIKI, NS_USER // don't mess with magic namespaces
                ] );

                $talk = array_filter( $namespaces, function ( $ns ) {
                        return MWNamespace::isTalk( $ns );
                } );

                // prefer non-talk pages
                $namespaces = array_diff( $namespaces, $talk );
                $namespaces = array_merge( $namespaces, $talk );

                // check default content model of each namespace
                foreach ( $namespaces as $ns ) {
                        if ( !isset( $wgNamespaceContentModels[$ns] ) ||
                                $wgNamespaceContentModels[$ns] === CONTENT_MODEL_WIKITEXT
                        ) {
                                $wikitextNS = $ns;

                                return $wikitextNS;
                        }
                }

                // give up
                // @todo Inside a test, we could skip the test as incomplete.
                //        But frequently, this is used in fixture setup.
                throw new MWException( "No namespace defaults to wikitext!" );
        }

        /**
         * Check, if $wgDiff3 is set and ready to merge
         * Will mark the calling test as skipped, if not ready
         *
         * @since 1.21
         */
        protected function markTestSkippedIfNoDiff3() {
                global $wgDiff3;

                # This check may also protect against code injection in
                # case of broken installations.
                Wikimedia\suppressWarnings();
                $haveDiff3 = $wgDiff3 && file_exists( $wgDiff3 );
                Wikimedia\restoreWarnings();

                if ( !$haveDiff3 ) {
                        $this->markTestSkipped( "Skip test, since diff3 is not configured" );
                }
        }

        /**
         * Check if $extName is a loaded PHP extension, will skip the
         * test whenever it is not loaded.
         *
         * @since 1.21
         * @param string $extName
         * @return bool
         */
        protected function checkPHPExtension( $extName ) {
                $loaded = extension_loaded( $extName );
                if ( !$loaded ) {
                        $this->markTestSkipped( "PHP extension '$extName' is not loaded, skipping." );
                }

                return $loaded;
        }

        /**
         * Skip the test if using the specified database type
         *
         * @param string $type Database type
         * @since 1.32
         */
        protected function markTestSkippedIfDbType( $type ) {
                if ( $this->db->getType() === $type ) {
                        $this->markTestSkipped( "The $type database type isn't supported for this test" );
                }
        }

        /**
         * Used as a marker to prevent wfResetOutputBuffers from breaking PHPUnit.
         * @param string $buffer
         * @return string
         */
        public static function wfResetOutputBuffersBarrier( $buffer ) {
                return $buffer;
        }

        /**
         * Create a temporary hook handler which will be reset by tearDown.
         * This replaces other handlers for the same hook.
         * @param string $hookName Hook name
         * @param mixed $handler Value suitable for a hook handler
         * @since 1.28
         */
        protected function setTemporaryHook( $hookName, $handler ) {
                $this->mergeMwGlobalArrayValue( 'wgHooks', [ $hookName => [ $handler ] ] );
        }

        /**
         * Check whether file contains given data.
         * @param string $fileName
         * @param string $actualData
         * @param bool $createIfMissing If true, and file does not exist, create it with given data
         *                              and skip the test.
         * @param string $msg
         * @since 1.30
         */
        protected function assertFileContains(
                $fileName,
                $actualData,
                $createIfMissing = true,
                $msg = ''
        ) {
                if ( $createIfMissing ) {
                        if ( !file_exists( $fileName ) ) {
                                file_put_contents( $fileName, $actualData );
                                $this->markTestSkipped( 'Data file $fileName does not exist' );
                        }
                } else {
                        self::assertFileExists( $fileName );
                }
                self::assertEquals( file_get_contents( $fileName ), $actualData, $msg );
        }

        /**
         * Edits or creates a page/revision
         * @param string $pageName Page title
         * @param string $text Content of the page
         * @param string $summary Optional summary string for the revision
         * @param int $defaultNs Optional namespace id
         * @return array Array as returned by WikiPage::doEditContent()
         */
        protected function editPage( $pageName, $text, $summary = '', $defaultNs = NS_MAIN ) {
                $title = Title::newFromText( $pageName, $defaultNs );
                $page = WikiPage::factory( $title );

                return $page->doEditContent( ContentHandler::makeContent( $text, $title ), $summary );
        }

        /**
         * Revision-deletes a revision.
         *
         * @param Revision|int $rev Revision to delete
         * @param array $value Keys are Revision::DELETED_* flags.  Values are 1 to set the bit, 0 to
         *   clear, -1 to leave alone.  (All other values also clear the bit.)
         * @param string $comment Deletion comment
         */
        protected function revisionDelete(
                $rev, array $value = [ Revision::DELETED_TEXT => 1 ], $comment = ''
        ) {
                if ( is_int( $rev ) ) {
                        $rev = Revision::newFromId( $rev );
                }
                RevisionDeleter::createList(
                        'revision', RequestContext::getMain(), $rev->getTitle(), [ $rev->getId() ]
                )->setVisibility( [
                        'value' => $value,
                        'comment' => $comment,
                ] );
        }
}