API: Fixes for AuthManager

[mediawiki.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;

/**
 * @since 1.18
 */
abstract class MediaWikiTestCase extends PHPUnit_Framework_TestCase {

        /**
         * 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 DatabaseBase
         * @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 = false;

        /**
         * 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 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();

                // NOTE: Usually, PHPUnitMaintClass::finalSetup already called this,
                // but let's make doubly sure.
                self::prepareServices( new GlobalVarConfig() );
        }

        /**
         * 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.
         */
        public static function prepareServices( Config $bootstrapConfig ) {
                static $servicesPrepared = false;

                if ( $servicesPrepared ) {
                        return;
                } else {
                        $servicesPrepared = true;
                }

                self::resetGlobalServices( $bootstrapConfig );
        }

        /**
         * 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 overrideMwServices() for that.
         *
         * @see MediaWikiServices::resetGlobalInstance()
         * @see prepareServices()
         * @see overrideMwServices()
         *
         * @param Config|null $bootstrapConfig The bootstrap config to use with the new
         *        MediaWikiServices.
         */
        protected static function resetGlobalServices( Config $bootstrapConfig = null ) {
                $oldServices = MediaWikiServices::getInstance();
                $oldConfigFactory = $oldServices->getConfigFactory();

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

                MediaWikiServices::resetGlobalInstance( $testConfig );

                self::$serviceLocator = MediaWikiServices::getInstance();
                self::installTestServices(
                        $oldConfigFactory,
                        self::$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' ];
                $objectCaches = [
                                CACHE_DB => $hashCache,
                                CACHE_ACCEL => $hashCache,
                                CACHE_MEMCACHED => $hashCache,
                                'apc' => $hashCache,
                                'xcache' => $hashCache,
                                'wincache' => $hashCache,
                        ] + $baseConfig->get( 'ObjectCaches' );

                $defaultOverrides->set( 'ObjectCaches', $objectCaches );
                $defaultOverrides->set( 'MainCacheType', CACHE_NONE );

                // 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 MediaWikiServices $newServices
         *
         * @throws MWException
         */
        private static function installTestServices(
                ConfigFactory $oldConfigFactory,
                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 ]
                        )
                );
        }

        /**
         * @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;

                JobQueueGroup::destroySingletons();
                ObjectCache::clear();
                FileBackendGroup::destroySingleton();

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

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

        public function run( PHPUnit_Framework_TestResult $result = null ) {
                // Reset all caches between tests.
                $this->doLightweightServiceReset();

                $needsResetDB = false;

                if ( $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();

                                if ( ( $this->db->getType() == 'oracle' || !self::$useTemporaryTables ) && self::$reuseDB ) {
                                        $this->resetDB( $this->db, $this->tablesUsed );
                                }
                        }

                        // 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->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_' . get_class( $this ) . '_' );
                $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' );
                        }
                }

                DeferredUpdates::clearPendingUpdates();
                ObjectCache::getMainWANInstance()->clearProcessCache();

                ob_start( 'MediaWikiTestCase::wfResetOutputBuffersBarrier' );
        }

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

        protected function tearDown() {
                global $wgRequest;

                $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' );
                        }
                }

                // Restore mw globals
                foreach ( $this->mwGlobals as $key => $value ) {
                        $GLOBALS[$key] = $value;
                }
                $this->mwGlobals = [];
                $this->restoreLoggers();

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

                // TODO: move global state into MediaWikiServices
                RequestContext::resetMain();
                MediaHandler::resetCache();
                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
         */
        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;
                        }
                );
        }

        /**
         * 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().
         *
         * @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() {}
         * </code>
         *
         * @param array|string $pairs Key to the global variable, or an array
         *  of key/value pairs.
         * @param mixed $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 ];
                }

                $this->stashMwGlobals( array_keys( $pairs ) );

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

        /**
         * 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.
         *
         * @throws Exception When trying to stash an unset global
         *
         * @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 ) ) {
                                if ( !array_key_exists( $globalKey, $GLOBALS ) ) {
                                        throw new Exception( "Global with key {$globalKey} doesn't exist and cant be stashed" );
                                }
                                // 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];
                                } else {
                                        try {
                                                $this->mwGlobals[$globalKey] = unserialize( serialize( $GLOBALS[$globalKey] ) );
                                        } catch ( Exception $e ) {
                                                $this->mwGlobals[$globalKey] = $GLOBALS[$globalKey];
                                        }
                                }
                        }
                }
        }

        /**
         * 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 $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 function overrideMwServices( Config $configOverrides = null, array $services = [] ) {
                if ( !$configOverrides ) {
                        $configOverrides = new HashConfig();
                }

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

                $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,
                        $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,
                        'wgContLang' => $langObj,
                ] );
        }

        /**
         * 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] = isset( $singletons['loggers'][$channel] )
                                        ? $singletons['loggers'][$channel] : null;
                        }
                        $singletons['loggers'][$channel] = $logger;
                } elseif ( $provider instanceof LegacySpi ) {
                        if ( !isset( $this->loggers[$channel] ) ) {
                                $this->loggers[$channel] = isset( $singletons[$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 $this->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 says it belongs to the Database group, it needs the database
                $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
         * @param string $pageName Page name
         * @param string $text Page's content
         * @return array Title object and page id
         */
        protected function insertPage( $pageName, $text = 'Sample page for unit test.' ) {
                $title = Title::newFromText( $pageName, 0 );

                $user = User::newFromName( 'UTSysop' );
                $comment = __METHOD__ . ': Sample page for unit test.';

                // Avoid memory leak...?
                // LinkCache::singleton()->clear();
                // Maybe.  But doing this absolutely breaks $title->isRedirect() when called during unit tests....

                $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() {
        }

        private function addCoreDBData() {
                if ( $this->db->getType() == 'oracle' ) {

                        # Insert 0 user to prevent FK violations
                        # Anonymous user
                        $this->db->insert( 'user', [
                                'user_id' => 0,
                                'user_name' => 'Anonymous' ], __METHOD__, [ 'IGNORE' ] );

                        # Insert 0 page to prevent FK violations
                        # Blank page
                        $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' ] );
                }

                User::resetIdByNameCache();

                // Make sysop user
                $user = User::newFromName( 'UTSysop' );

                if ( $user->idForName() == 0 ) {
                        $user->addToDatabase();
                        TestUser::setPasswordForUser( $user, 'UTSysopPassword' );
                        $user->addGroup( 'sysop' );
                        $user->addGroup( 'bureaucrat' );
                }

                // Make 1 page with 1 revision
                $page = WikiPage::factory( Title::newFromText( 'UTPage' ) );
                if ( $page->getId() == 0 ) {
                        $page->doEditContent(
                                new WikitextContent( 'UTContent' ),
                                'UTPageSummary',
                                EDIT_NEW,
                                false,
                                $user
                        );

                        // 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).
         *
         * @since 1.21
         */
        public static function teardownTestDB() {
                global $wgJobClasses;

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

                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;
        }

        /**
         * Setups a database with 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.
         *
         * Clones all tables in the given database (whatever database that connection has
         * open), to versions with the test prefix.
         *
         * @param DatabaseBase $db Database to use
         * @param string $prefix Prefix to use for test tables
         * @return bool True if tables were cloned, false if only the prefix was changed
         */
        protected static function setupDatabaseWithTestPrefix( DatabaseBase $db, $prefix ) {
                $tablesCloned = self::listTables( $db );
                $dbClone = new CloneDatabase( $db, $tablesCloned, $prefix );
                $dbClone->useTemporaryTables( self::$useTemporaryTables );

                if ( ( $db->getType() == 'oracle' || !self::$useTemporaryTables ) && self::$reuseDB ) {
                        CloneDatabase::changePrefix( $prefix );

                        return false;
                } else {
                        $dbClone->cloneTableStructure();
                        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 );
                }
        }

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

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

                // TODO: the below should be re-written as soon as LBFactory, LoadBalancer,
                // and DatabaseBase 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;' );
                }
        }

        /**
         * Clones the External Store database(s) for testing
         *
         * @param string $testPrefix Prefix for test tables
         */
        protected static function setupExternalStoreTestDBs( $testPrefix ) {
                $connections = self::getExternalStoreDatabaseConnections();
                foreach ( $connections as $dbw ) {
                        // Hack: cloneTableStructure sets $wgDBprefix to the unit test
                        // prefix,.  Even though listTables now uses tablePrefix, that
                        // itself is populated from $wgDBprefix by default.

                        // We have to set it back, or we won't find the original 'blobs'
                        // table to copy.

                        $dbw->tablePrefix( self::$oldTablePrefix );
                        self::setupDatabaseWithTestPrefix( $dbw, $testPrefix );
                }
        }

        /**
         * Gets master database connections for all of the ExternalStoreDB
         * stores configured in $wgDefaultExternalStore.
         *
         * @return array Array of DatabaseBase master connections
         */

        protected static function getExternalStoreDatabaseConnections() {
                global $wgDefaultExternalStore;

                $externalStoreDB = ExternalStore::getStoreObject( 'DB' );
                $defaultArray = (array) $wgDefaultExternalStore;
                $dbws = [];
                foreach ( $defaultArray as $url ) {
                        if ( strpos( $url, 'DB://' ) === 0 ) {
                                list( $proto, $cluster ) = explode( '://', $url, 2 );
                                $dbw = $externalStoreDB->getMaster( $cluster );
                                $dbws[] = $dbw;
                        }
                }

                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;
        }

        /**
         * Empty all tables so they can be repopulated for tests
         *
         * @param DatabaseBase $db|null Database to reset
         * @param array $tablesUsed Tables to reset
         */
        private function resetDB( $db, $tablesUsed ) {
                if ( $db ) {
                        $userTables = [ 'user', 'user_groups', 'user_properties' ];
                        $coreDBDataTables = array_merge( $userTables, [ 'page', 'revision' ] );

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

                                // Totally clear User class in-process cache to avoid CAS errors
                                TestingAccessWrapper::newFromClass( 'User' )
                                        ->getInProcessCache()
                                        ->clear();
                        }

                        $truncate = in_array( $db->getType(), [ 'oracle', 'mysql' ] );
                        foreach ( $tablesUsed as $tbl ) {
                                // TODO: reset interwiki table to its original content.
                                if ( $tbl == 'interwiki' ) {
                                        continue;
                                }

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

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

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

        /**
         * @since 1.18
         *
         * @param string $func
         * @param array $args
         *
         * @return mixed
         * @throws MWException
         */
        public function __call( $func, $args ) {
                static $compatibility = [
                        'assertEmpty' => 'assertEmpty2', // assertEmpty was added in phpunit 3.7.32
                ];

                if ( isset( $compatibility[$func] ) ) {
                        return call_user_func_array( [ $this, $compatibility[$func] ], $args );
                } else {
                        throw new MWException( "Called non-existent $func method on "
                                . get_class( $this ) );
                }
        }

        /**
         * Used as a compatibility method for phpunit < 3.7.32
         * @param string $value
         * @param string $msg
         */
        private function assertEmpty2( $value, $msg ) {
                $this->assertTrue( $value == '', $msg );
        }

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

        private static function isNotUnittest( $table ) {
                return strpos( $table, 'unittest_' ) !== 0;
        }

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

                if ( $db->getType() === 'mysql' ) {
                        # bug 43571: cannot clone VIEWs under MySQL
                        $views = $db->listViews( $prefix, __METHOD__ );
                        $tables = array_diff( $tables, $views );
                }
                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;
        }

        /**
         * @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];
                }
        }

        /**
         * @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 ) {
                MediaWiki\suppressWarnings();
                wfDeprecated( $function );
                MediaWiki\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.
         *
         * @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 $expectedRows ) {
                if ( !$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_SLAVE );

                $res = $db->select( $table, $fields, $condition, wfGetCaller(), [ 'ORDER BY' => $fields ] );
                $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 ) ? 1 : -1;
                        }
                );
        }

        /**
         * 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.
                MediaWiki\suppressWarnings();
                $haveDiff3 = $wgDiff3 && file_exists( $wgDiff3 );
                MediaWiki\restoreWarnings();

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

        /**
         * Check whether we have the 'gzip' commandline utility, will skip
         * the test whenever "gzip -V" fails.
         *
         * Result is cached at the process level.
         *
         * @return bool
         *
         * @since 1.21
         */
        protected function checkHasGzip() {
                static $haveGzip;

                if ( $haveGzip === null ) {
                        $retval = null;
                        wfShellExec( 'gzip -V', $retval );
                        $haveGzip = ( $retval === 0 );
                }

                if ( !$haveGzip ) {
                        $this->markTestSkipped( "Skip test, requires the gzip utility in PATH" );
                }

                return $haveGzip;
        }

        /**
         * 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;
        }

        /**
         * Asserts that the given string is a valid HTML snippet.
         * Wraps the given string in the required top level tags and
         * then calls assertValidHtmlDocument().
         * The snippet is expected to be HTML 5.
         *
         * @since 1.23
         *
         * @note Will mark the test as skipped if the "tidy" module is not installed.
         * @note This ignores $wgUseTidy, so we can check for valid HTML even (and especially)
         *        when automatic tidying is disabled.
         *
         * @param string $html An HTML snippet (treated as the contents of the body tag).
         */
        protected function assertValidHtmlSnippet( $html ) {
                $html = '<!DOCTYPE html><html><head><title>test</title></head><body>' . $html . '</body></html>';
                $this->assertValidHtmlDocument( $html );
        }

        /**
         * Asserts that the given string is valid HTML document.
         *
         * @since 1.23
         *
         * @note Will mark the test as skipped if the "tidy" module is not installed.
         * @note This ignores $wgUseTidy, so we can check for valid HTML even (and especially)
         *        when automatic tidying is disabled.
         *
         * @param string $html A complete HTML document
         */
        protected function assertValidHtmlDocument( $html ) {
                // Note: we only validate if the tidy PHP extension is available.
                // In case wgTidyInternal is false, MWTidy would fall back to the command line version
                // of tidy. In that case however, we can not reliably detect whether a failing validation
                // is due to malformed HTML, or caused by tidy not being installed as a command line tool.
                // That would cause all HTML assertions to fail on a system that has no tidy installed.
                if ( !$GLOBALS['wgTidyInternal'] || !MWTidy::isEnabled() ) {
                        $this->markTestSkipped( 'Tidy extension not installed' );
                }

                $errorBuffer = '';
                MWTidy::checkErrors( $html, $errorBuffer );
                $allErrors = preg_split( '/[\r\n]+/', $errorBuffer );

                // Filter Tidy warnings which aren't useful for us.
                // Tidy eg. often cries about parameters missing which have actually
                // been deprecated since HTML4, thus we should not care about them.
                $errors = preg_grep(
                        '/^(.*Warning: (trimming empty|.* lacks ".*?" attribute).*|\s*)$/m',
                        $allErrors, PREG_GREP_INVERT
                );

                $this->assertEmpty( $errors, implode( "\n", $errors ) );
        }

        /**
         * @param array $matcher
         * @param string $actual
         * @param bool $isHtml
         *
         * @return bool
         */
        private static function tagMatch( $matcher, $actual, $isHtml = true ) {
                $dom = PHPUnit_Util_XML::load( $actual, $isHtml );
                $tags = PHPUnit_Util_XML::findNodes( $dom, $matcher, $isHtml );
                return count( $tags ) > 0 && $tags[0] instanceof DOMNode;
        }

        /**
         * Note: we are overriding this method to remove the deprecated error
         * @see https://phabricator.wikimedia.org/T71505
         * @see https://github.com/sebastianbergmann/phpunit/issues/1292
         * @deprecated
         *
         * @param array $matcher
         * @param string $actual
         * @param string $message
         * @param bool $isHtml
         */
        public static function assertTag( $matcher, $actual, $message = '', $isHtml = true ) {
                // trigger_error(__METHOD__ . ' is deprecated', E_USER_DEPRECATED);

                self::assertTrue( self::tagMatch( $matcher, $actual, $isHtml ), $message );
        }

        /**
         * @see MediaWikiTestCase::assertTag
         * @deprecated
         *
         * @param array $matcher
         * @param string $actual
         * @param string $message
         * @param bool $isHtml
         */
        public static function assertNotTag( $matcher, $actual, $message = '', $isHtml = true ) {
                // trigger_error(__METHOD__ . ' is deprecated', E_USER_DEPRECATED);

                self::assertFalse( self::tagMatch( $matcher, $actual, $isHtml ), $message );
        }

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

}