MediaWikiTestCase.php

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<?php
use MediaWiki\Logger\LegacySpi;
use MediaWiki\Logger\LoggerFactory;
use MediaWiki\Logger\MonologSpi;
use Psr\Log\LoggerInterface;

abstract class MediaWikiTestCase extends PHPUnit_Framework_TestCase {
    private $called = [];

    public static $users;

    protected $db;

    protected $tablesUsed = []; // tables with data

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

    private $phpErrorLevel;

    private $tmpFiles = [];

    private $mwGlobals = [];

    private $loggers = [];

    const DB_PREFIX = 'unittest_';
    const ORA_DB_PREFIX = 'ut_';

    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 function run( PHPUnit_Framework_TestResult $result = null ) {
        /* Some functions require some kind of caching, and will end up using the db,
         * which we can't allow, as that would open a new connection for mysql.
         * Replace with a HashBag. They would not be going to persist anyway.
         */
        ObjectCache::$instances[CACHE_DB] = new HashBagOStuff;

        // Sandbox APC by replacing with in-process hash instead.
        // Ensures values are removed between tests.
        ObjectCache::$instances['apc'] =
        ObjectCache::$instances['xcache'] =
        ObjectCache::$instances['wincache'] = new HashBagOStuff;

        $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 );
        }
    }

    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;
    }

    public function usesTemporaryTables() {
        return self::$useTemporaryTables;
    }

    protected function getNewTempFile() {
        $fileName = tempnam( wfTempDir(), 'MW_PHPUnit_' . get_class( $this ) . '_' );
        $this->tmpFiles[] = $fileName;

        return $fileName;
    }

    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();
        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();
    }

    final public function testMediaWikiTestCaseParentSetupCalled() {
        $this->assertArrayHasKey( 'setUp', $this->called,
            static::class . '::setUp() must call parent::setUp()'
        );
    }

    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;
        }
    }

    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!
                try {
                    $this->mwGlobals[$globalKey] = unserialize( serialize( $GLOBALS[$globalKey] ) );
                }
                    // NOTE; some things such as Closures are not serializable
                    // in this case just set the value!
                catch ( Exception $e ) {
                    $this->mwGlobals[$globalKey] = $GLOBALS[$globalKey];
                }
            }
        }
    }

    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 );
    }

    public function setUserLang( $lang ) {
        RequestContext::getMain()->setLanguage( $lang );
        $this->setMwGlobals( 'wgLang', RequestContext::getMain()->getLanguage() );
    }

    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,
        ] );
    }

    protected function setLogger( $channel, LoggerInterface $logger ) {
        $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;
    }

    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 = [];
    }

    public function dbPrefix() {
        return $this->db->getType() == 'oracle' ? self::ORA_DB_PREFIX : self::DB_PREFIX;
    }

    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;
    }

    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.';

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

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

    public function addDBDataOnce() {
    }

    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( '' );
            }
        }
    }

    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;
    }

    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;
        }
    }

    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 );
        }
    }

    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;
        }

        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;' );
        }
    }

    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 );
        }
    }

    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;
    }

    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;
    }

    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();
            }
        }
    }

    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 ) );
        }
    }

    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;
    }

    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;
    }

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

    public function getCliArg( $offset ) {
        if ( isset( PHPUnitMaintClass::$additionalOptions[$offset] ) ) {
            return PHPUnitMaintClass::$additionalOptions[$offset];
        }
    }

    public function setCliArg( $offset, $value ) {
        PHPUnitMaintClass::$additionalOptions[$offset] = $value;
    }

    public function hideDeprecated( $function ) {
        MediaWiki\suppressWarnings();
        wfDeprecated( $function );
        MediaWiki\restoreWarnings();
    }

    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)" );
    }

    protected function arrayWrap( array $elements ) {
        return array_map(
            function ( $element ) {
                return [ $element ];
            },
            $elements
        );
    }

    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 ) )
        );
    }

    protected function assertHTMLEquals( $expected, $actual, $msg = '' ) {
        $expected = str_replace( '>', ">\n", $expected );
        $actual = str_replace( '>', ">\n", $actual );

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

    protected function objectAssociativeSort( array &$array ) {
        uasort(
            $array,
            function ( $a, $b ) {
                return serialize( $a ) > serialize( $b ) ? 1 : -1;
            }
        );
    }

    protected static function stripStringKeys( &$r ) {
        if ( !is_array( $r ) ) {
            return;
        }

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

    protected function assertTypeOrValue( $type, $actual, $value = false, $message = '' ) {
        if ( $actual === $value ) {
            $this->assertTrue( true, $message );
        } else {
            $this->assertType( $type, $actual, $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 );
        }
    }

    protected function isWikitextNS( $ns ) {
        global $wgNamespaceContentModels;

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

        return true;
    }

    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!" );
    }

    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" );
        }
    }

    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;
    }

    protected function checkPHPExtension( $extName ) {
        $loaded = extension_loaded( $extName );
        if ( !$loaded ) {
            $this->markTestSkipped( "PHP extension '$extName' is not loaded, skipping." );
        }

        return $loaded;
    }

    protected function assertValidHtmlSnippet( $html ) {
        $html = '<!DOCTYPE html><html><head><title>test</title></head><body>' . $html . '</body></html>';
        $this->assertValidHtmlDocument( $html );
    }

    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 ) );
    }

    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;
    }

    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 );
    }

    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 );
    }

    public static function wfResetOutputBuffersBarrier( $buffer ) {
        return $buffer;
    }

}