diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 02e24fb..445214c 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -26,6 +26,8 @@ jobs:
 
     - name: Install dependencies
       run: composer install --prefer-dist --no-progress --no-interaction --no-suggest
+    - name: Run PHPStan
+      run: php vendor/bin/phpstan
 
     - name: Run test suite
       run: |
diff --git a/composer.json b/composer.json
index ee7c669..a447850 100644
--- a/composer.json
+++ b/composer.json
@@ -27,8 +27,9 @@
         "yiisoft/yii2-app-advanced": "dev-master",
         "codeception/verify": "^3.0",
         "codemix/yii2-localeurls": "^1.7",
-        "codeception/module-asserts": "^3.0",
-        "codeception/module-filesystem": "^3.0"
+        "codeception/module-asserts": ">= 3.0",
+        "codeception/module-filesystem": "> 3.0",
+        "phpstan/phpstan": "^1.10"
     },
     "autoload":{
         "classmap": ["src/"]
diff --git a/phpstan.neon b/phpstan.neon
new file mode 100644
index 0000000..efda0f0
--- /dev/null
+++ b/phpstan.neon
@@ -0,0 +1,20 @@
+#includes:
+#    - phpstan-baseline.neon
+parameters:
+    reportUnmatchedIgnoredErrors: true
+    dynamicConstantNames:
+      - CONSOLE
+      - YII_DEBUG
+    level: 5
+    paths:
+      - src
+    checkMaybeUndefinedVariables: true
+    checkGenericClassInNonGenericObjectType: false
+    ignoreErrors:
+        # All Yii setters accept `null` but their phpdoc is incorrect.
+        - message: '~^Parameter #1 \$(.+) of method yii\\web\\Request::set(.+)\(\) expects (.+), null given.$~'
+          path: 'src/'
+        - message: '~^Variable \$_COOKIE in isset\(\) always exists and is not nullable.$~'
+          path: 'src/'
+    stubFiles:
+        - tests/Yii.stub
diff --git a/src/Codeception/Lib/Connector/Yii2.php b/src/Codeception/Lib/Connector/Yii2.php
index d18a3a3..b7c7519 100644
--- a/src/Codeception/Lib/Connector/Yii2.php
+++ b/src/Codeception/Lib/Connector/Yii2.php
@@ -7,6 +7,8 @@
 use Codeception\Util\Debug;
 use Symfony\Component\BrowserKit\AbstractBrowser as Client;
 use Symfony\Component\BrowserKit\Cookie;
+use Symfony\Component\BrowserKit\CookieJar;
+use Symfony\Component\BrowserKit\History;
 use Symfony\Component\BrowserKit\Response;
 use Yii;
 use yii\base\ExitException;
@@ -15,8 +17,10 @@
 use yii\mail\MessageInterface;
 use yii\web\Application;
 use yii\web\ErrorHandler;
+use yii\web\IdentityInterface;
 use yii\web\Request;
 use yii\web\Response as YiiResponse;
+use yii\web\User;
 
 class Yii2 extends Client
 {
@@ -81,23 +85,22 @@ class Yii2 extends Client
     /**
      * @var bool whether to close the session in between requests inside a single test, if recreateApplication is set to true
      */
-    public $closeSessionOnRecreateApplication = true;
+    public bool $closeSessionOnRecreateApplication = true;
 
     /**
-     * @var string The FQN of the application class to use. In a default Yii setup, should be either `yii\web\Application`
+     * @var class-string The FQN of the application class to use. In a default Yii setup, should be either `yii\web\Application`
      *             or `yii\console\Application`
      */
-    public $applicationClass = null;
+    public string|null $applicationClass = null;
 
 
-    private $emails = [];
+    private array $emails = [];
 
     /**
-     * @return \yii\web\Application
-     *
      * @deprecated since 2.5, will become protected in 3.0. Directly access to \Yii::$app if you need to interact with it.
+     * @internal
      */
-    public function getApplication()
+    public function getApplication(): \yii\base\Application
     {
         if (!isset(Yii::$app)) {
             $this->startApp();
@@ -105,10 +108,7 @@ public function getApplication()
         return Yii::$app;
     }
 
-    /**
-     * @param bool $closeSession
-     */
-    public function resetApplication($closeSession = true)
+    public function resetApplication(bool $closeSession = true): void
     {
         codecept_debug('Destroying application');
         if (true === $closeSession) {
@@ -127,14 +127,14 @@ public function resetApplication($closeSession = true)
     /**
      * Finds and logs in a user
      * @internal
-     * @param $user
      * @throws ConfigurationException
      * @throws \RuntimeException
      */
-    public function findAndLoginUser($user)
+    public function findAndLoginUser(int|string|IdentityInterface $user): void
     {
         $app = $this->getApplication();
-        if (!$app->has('user')) {
+        $user = $app->get('user');
+        if (!$user instanceof User) {
             throw new ConfigurationException('The user component is not configured');
         }
 
@@ -142,25 +142,13 @@ public function findAndLoginUser($user)
             $identity = $user;
         } else {
             // class name implementing IdentityInterface
-            $identityClass = $app->user->identityClass;
+            $identityClass = $user->identityClass;
             $identity = call_user_func([$identityClass, 'findIdentity'], $user);
             if (!isset($identity)) {
                 throw new \RuntimeException('User not found');
             }
         }
-        $app->user->login($identity);
-    }
-
-    /**
-     * Masks a value
-     * @internal
-     * @param string $val
-     * @return string
-     * @see \yii\base\Security::maskToken
-     */
-    public function maskToken($val)
-    {
-        return $this->getApplication()->security->maskToken($val);
+        $user->login($identity);
     }
 
     /**
@@ -169,7 +157,7 @@ public function maskToken($val)
      * @param string $value The value of the cookie
      * @return string The value to send to the browser
      */
-    public function hashCookieData($name, $value)
+    public function hashCookieData($name, $value): string
     {
         $app = $this->getApplication();
         if (!$app->request->enableCookieValidation) {
@@ -182,7 +170,7 @@ public function hashCookieData($name, $value)
      * @internal
      * @return array List of regex patterns for recognized domain names
      */
-    public function getInternalDomains()
+    public function getInternalDomains(): array
     {
         /** @var \yii\web\UrlManager $urlManager */
         $urlManager = $this->getApplication()->urlManager;
@@ -202,7 +190,7 @@ public function getInternalDomains()
      * @internal
      * @return array List of sent emails
      */
-    public function getEmails()
+    public function getEmails(): array
     {
         return $this->emails;
     }
@@ -211,7 +199,7 @@ public function getEmails()
      * Deletes all stored emails.
      * @internal
      */
-    public function clearEmails()
+    public function clearEmails(): void
     {
         $this->emails = [];
     }
@@ -230,11 +218,8 @@ public function getComponent($name)
 
     /**
      * Getting domain regex from rule host template
-     *
-     * @param string $template
-     * @return string
      */
-    private function getDomainRegex($template)
+    private function getDomainRegex(string $template): string
     {
         if (preg_match('#https?://(.*)#', $template, $matches)) {
             $template = $matches[1];
@@ -259,24 +244,13 @@ function ($matches) use (&$parameters) {
     /**
      * Gets the name of the CSRF param.
      * @internal
-     * @return string
      */
-    public function getCsrfParamName()
+    public function getCsrfParamName(): string
     {
         return $this->getApplication()->request->csrfParam;
     }
 
-    /**
-     * @internal
-     * @param $params
-     * @return mixed
-     */
-    public function createUrl($params)
-    {
-        return is_array($params) ?$this->getApplication()->getUrlManager()->createUrl($params) : $params;
-    }
-
-    public function startApp(\yii\log\Logger $logger = null)
+    public function startApp(\yii\log\Logger $logger = null): void
     {
         codecept_debug('Starting application');
         $config = require($this->configFile);
@@ -306,12 +280,9 @@ public function startApp(\yii\log\Logger $logger = null)
     }
 
     /**
-     *
      * @param \Symfony\Component\BrowserKit\Request $request
-     *
-     * @return \Symfony\Component\BrowserKit\Response
      */
-    public function doRequest(object $request)
+    public function doRequest(object $request): \Symfony\Component\BrowserKit\Response
     {
         $_COOKIE = $request->getCookies();
         $_SERVER = $request->getServer();
@@ -343,6 +314,9 @@ public function doRequest(object $request)
         $this->beforeRequest();
 
         $app = $this->getApplication();
+        if (!$app instanceof Application) {
+            throw new ConfigurationException("Application is not a web application");
+        }
 
         // disabling logging. Logs are slowing test execution down
         foreach ($app->log->targets as $target) {
@@ -407,14 +381,13 @@ protected function revertErrorHandler()
 
     /**
      * Encodes the cookies and adds them to the headers.
-     * @param \yii\web\Response $response
      * @throws \yii\base\InvalidConfigException
      */
     protected function encodeCookies(
         YiiResponse $response,
         Request $request,
         Security $security
-    ) {
+    ): void {
         if ($request->enableCookieValidation) {
             $validationKey = $request->cookieValidationKey;
         }
@@ -422,7 +395,8 @@ protected function encodeCookies(
         foreach ($response->getCookies() as $cookie) {
             /** @var \yii\web\Cookie $cookie */
             $value = $cookie->value;
-            if ($cookie->expire != 1 && isset($validationKey)) {
+            // Expire = 1 means we're removing the cookie
+            if ($cookie->expire !== 1 && isset($validationKey)) {
                 $data = version_compare(Yii::getVersion(), '2.0.2', '>')
                     ? [$cookie->name, $cookie->value]
                     : $cookie->value;
@@ -443,10 +417,10 @@ protected function encodeCookies(
 
     /**
      * Replace mailer with in memory mailer
-     * @param array $config Original configuration
-     * @return array New configuration
+     * @param array<string, mixed> $config Original configuration
+     * @return array<string, mixed> New configuration
      */
-    protected function mockMailer(array $config)
+    protected function mockMailer(array $config): array
     {
         // options that make sense for mailer mock
         $allowedOptions = [
@@ -489,9 +463,10 @@ public function restart(): void
     /**
      * Return an assoc array with the client context: cookieJar, history.
      *
-     * @return array
+     * @internal
+     * @return array{ cookieJar: CookieJar, history: History }
      */
-    public function getContext()
+    public function getContext(): array
     {
         return [
             'cookieJar' => $this->cookieJar,
@@ -499,20 +474,12 @@ public function getContext()
         ];
     }
 
-    /**
-     * Reset the client context: empty cookieJar and history.
-     */
-    public function removeContext()
-    {
-        parent::restart();
-    }
-
     /**
      * Set the context, see getContext().
      *
-     * @param array $context
+     * @param array{ cookieJar: CookieJar, history: History } $context
      */
-    public function setContext(array $context)
+    public function setContext(array $context): void
     {
         $this->cookieJar = $context['cookieJar'];
         $this->history = $context['history'];
@@ -522,10 +489,11 @@ public function setContext(array $context)
      * This functions closes the session of the application, if the application exists and has a session.
      * @internal
      */
-    public function closeSession()
+    public function closeSession(): void
     {
-        if (isset(\Yii::$app) && \Yii::$app->has('session', true)) {
-            \Yii::$app->session->close();
+        $app = \Yii::$app;
+        if ($app instanceof \yii\web\Application && $app->has('session', true)) {
+            $app->session->close();
         }
     }
 
@@ -533,7 +501,7 @@ public function closeSession()
      * Resets the applications' response object.
      * The method used depends on the module configuration.
      */
-    protected function resetResponse(Application $app)
+    protected function resetResponse(Application $app): void
     {
         $method = $this->responseCleanMethod;
         // First check the current response object.
@@ -566,7 +534,7 @@ protected function resetResponse(Application $app)
         }
     }
 
-    protected function resetRequest(Application $app)
+    protected function resetRequest(Application $app): void
     {
         $method = $this->requestCleanMethod;
         $request = $app->request;
@@ -596,8 +564,8 @@ protected function resetRequest(Application $app)
                 $request->setScriptFile(null);
                 $request->setScriptUrl(null);
                 $request->setUrl(null);
-                $request->setPort(null);
-                $request->setSecurePort(null);
+                $request->setPort(0);
+                $request->setSecurePort(0);
                 $request->setAcceptableContentTypes(null);
                 $request->setAcceptableLanguages(null);
 
@@ -610,7 +578,7 @@ protected function resetRequest(Application $app)
     /**
      * Called before each request, preparation happens here.
      */
-    protected function beforeRequest()
+    protected function beforeRequest(): void
     {
         if ($this->recreateApplication) {
             $this->resetApplication($this->closeSessionOnRecreateApplication);
@@ -619,6 +587,9 @@ protected function beforeRequest()
 
         $application = $this->getApplication();
 
+        if (!$application instanceof Application) {
+            throw new ConfigurationException('Application must be an instance of web application when doing requests');
+        }
         $this->resetResponse($application);
         $this->resetRequest($application);
 
diff --git a/src/Codeception/Lib/Connector/Yii2/ConnectionWatcher.php b/src/Codeception/Lib/Connector/Yii2/ConnectionWatcher.php
index eae5382..291c921 100644
--- a/src/Codeception/Lib/Connector/Yii2/ConnectionWatcher.php
+++ b/src/Codeception/Lib/Connector/Yii2/ConnectionWatcher.php
@@ -13,10 +13,10 @@
  */
 class ConnectionWatcher
 {
-    private $handler;
+    private \Closure $handler;
 
     /** @var Connection[] */
-    private $connections = [];
+    private array $connections = [];
 
     public function __construct()
     {
@@ -27,27 +27,25 @@ public function __construct()
         };
     }
 
-    protected function connectionOpened(Connection $connection)
+    protected function connectionOpened(Connection $connection): void
     {
         $this->debug('Connection opened!');
-        if ($connection instanceof Connection) {
-            $this->connections[] = $connection;
-        }
+        $this->connections[] = $connection;
     }
 
-    public function start()
+    public function start(): void
     {
         Event::on(Connection::class, Connection::EVENT_AFTER_OPEN, $this->handler);
         $this->debug('watching new connections');
     }
 
-    public function stop()
+    public function stop(): void
     {
         Event::off(Connection::class, Connection::EVENT_AFTER_OPEN, $this->handler);
         $this->debug('no longer watching new connections');
     }
 
-    public function closeAll()
+    public function closeAll(): void
     {
         $count = count($this->connections);
         $this->debug("closing all ($count) connections");
@@ -56,7 +54,7 @@ public function closeAll()
         }
     }
 
-    protected function debug($message)
+    protected function debug($message): void
     {
         $title = (new \ReflectionClass($this))->getShortName();
         if (is_array($message) or is_object($message)) {
diff --git a/src/Codeception/Lib/Connector/Yii2/Logger.php b/src/Codeception/Lib/Connector/Yii2/Logger.php
index 3135962..b229f32 100644
--- a/src/Codeception/Lib/Connector/Yii2/Logger.php
+++ b/src/Codeception/Lib/Connector/Yii2/Logger.php
@@ -2,32 +2,30 @@
 namespace Codeception\Lib\Connector\Yii2;
 
 use Codeception\Util\Debug;
+use yii\helpers\VarDumper;
 
 class Logger extends \yii\log\Logger
 {
-    /**
-     * @var \SplQueue
-     */
-    private $logQueue;
-
-    /**
-     * @var int
-     */
-    private $maxLogItems;
+    private \SplQueue $logQueue;
 
-    public function __construct($maxLogItems = 5, $config = [])
+    public function __construct(private int $maxLogItems = 5, $config = [])
     {
         parent::__construct($config);
         $this->logQueue = new \SplQueue();
-        $this->maxLogItems = $maxLogItems;
     }
 
-    public function init()
+    public function init(): void
     {
         // overridden to prevent register_shutdown_function
     }
 
-    public function log($message, $level, $category = 'application')
+    /**
+     * @param string|array<mixed>|\yii\base\Exception $message
+     * @param $level
+     * @param $category
+     * @return void
+     */
+    public function log($message, $level, $category = 'application'): void
     {
         if (!in_array($level, [
             \yii\log\Logger::LEVEL_INFO,
@@ -36,7 +34,7 @@ public function log($message, $level, $category = 'application')
         ])) {
             return;
         }
-        if (strpos($category, 'yii\db\Command')===0) {
+        if (str_starts_with($category, 'yii\db\Command')) {
             return; // don't log queries
         }
 
@@ -45,7 +43,7 @@ public function log($message, $level, $category = 'application')
             $message = $message->__toString();
         }
 
-        $logMessage = "[$category] " . \yii\helpers\VarDumper::export($message);
+        $logMessage = "[$category] " . VarDumper::export($message);
 
         Debug::debug($logMessage);
 
@@ -55,10 +53,7 @@ public function log($message, $level, $category = 'application')
         }
     }
 
-    /**
-     * @return string
-     */
-    public function getAndClearLog()
+    public function getAndClearLog(): string
     {
         $completeStr = '';
         foreach ($this->logQueue as $item) {
diff --git a/src/Codeception/Lib/Connector/Yii2/TransactionForcer.php b/src/Codeception/Lib/Connector/Yii2/TransactionForcer.php
index 060b8a1..fbc08f2 100644
--- a/src/Codeception/Lib/Connector/Yii2/TransactionForcer.php
+++ b/src/Codeception/Lib/Connector/Yii2/TransactionForcer.php
@@ -3,6 +3,7 @@
 
 namespace Codeception\Lib\Connector\Yii2;
 
+use Codeception\Util\Debug;
 use yii\base\Event;
 use yii\db\Connection;
 use yii\db\Transaction;
@@ -30,7 +31,7 @@ public function __construct(
     }
 
 
-    protected function connectionOpened(Connection $connection)
+    protected function connectionOpened(Connection $connection): void
     {
         parent::connectionOpened($connection);
         /**
@@ -80,7 +81,7 @@ protected function connectionOpened(Connection $connection)
         $this->transactions[$key] = $connection->beginTransaction();
     }
 
-    public function rollbackAll()
+    public function rollbackAll(): void
     {
         /** @var Transaction $transaction */
         foreach ($this->transactions as $transaction) {
diff --git a/src/Codeception/Module/Yii2.php b/src/Codeception/Module/Yii2.php
index fb1c408..06d09d8 100644
--- a/src/Codeception/Module/Yii2.php
+++ b/src/Codeception/Module/Yii2.php
@@ -1,25 +1,25 @@
 <?php
 namespace Codeception\Module;
 
-use Codeception\Configuration;
 use Codeception\Exception\ConfigurationException;
 use Codeception\Exception\ModuleConfigException;
 use Codeception\Exception\ModuleException;
 use Codeception\Lib\Connector\Yii2 as Yii2Connector;
+use Codeception\Lib\Connector\Yii2\ConnectionWatcher;
+use Codeception\Lib\Connector\Yii2\Logger;
+use Codeception\Lib\Connector\Yii2\TransactionForcer;
 use Codeception\Lib\Framework;
 use Codeception\Lib\Interfaces\ActiveRecord;
 use Codeception\Lib\Interfaces\MultiSession;
 use Codeception\Lib\Interfaces\PartedModule;
 use Codeception\TestInterface;
-use Codeception\Util\Debug;
 use Symfony\Component\DomCrawler\Crawler as SymfonyCrawler;
 use Yii;
-use yii\base\Event;
-use yii\db\ActiveRecordInterface;
-use yii\db\Connection;
-use yii\db\QueryInterface;
-use yii\db\Transaction;
+use yii\base\Security;
+use yii\db\ActiveQueryInterface;
 use yii\helpers\Url;
+use yii\web\Application;
+use yii\web\IdentityInterface;
 
 /**
  * This module provides integration with [Yii framework](https://www.yiiframework.com/) (2.0).
@@ -164,9 +164,8 @@
  * Maintainer: **samdark**
  * Stability: **stable**
  *
- * @property \Codeception\Lib\Connector\Yii2 $client
  */
-class Yii2 extends Framework implements ActiveRecord, MultiSession, PartedModule
+final class Yii2 extends Framework implements ActiveRecord, MultiSession, PartedModule
 {
     /**
      * Application config file must be set.
@@ -196,29 +195,32 @@ class Yii2 extends Framework implements ActiveRecord, MultiSession, PartedModule
 
     /**
      * Helper to manage database connections
-     * @var Yii2Connector\ConnectionWatcher
      */
-    private $connectionWatcher;
+    private ConnectionWatcher $connectionWatcher;
 
     /**
      * Helper to force database transaction
-     * @var Yii2Connector\TransactionForcer
      */
-    private $transactionForcer;
+    private TransactionForcer $transactionForcer;
 
     /**
      * @var array The contents of $_SERVER upon initialization of this object.
      * This is only used to restore it upon object destruction.
      * It MUST not be used anywhere else.
      */
-    private $server;
+    private array $server;
 
-    /**
-     * @var Yii2Connector\Logger
-     */
-    private $yiiLogger;
+    private Logger $yiiLogger;
 
-    public function _initialize()
+    private function getClient(): \Codeception\Lib\Connector\Yii2|null
+    {
+        if (isset($this->client) && !$this->client instanceof \Codeception\Lib\Connector\Yii2) {
+            throw new \RuntimeException('The Yii2 module must be used with the Yii2 browser client');
+        }
+        return $this->client;
+    }
+
+    public function _initialize(): void
     {
         if ($this->config['transaction'] === null) {
             $this->config['transaction'] = $this->backupConfig['transaction'] = $this->config['cleanup'];
@@ -234,13 +236,13 @@ public function _initialize()
      * Module configuration changed inside a test.
      * We always re-create the application.
      */
-    protected function onReconfigure()
+    protected function onReconfigure(): void
     {
         parent::onReconfigure();
-        $this->client->resetApplication();
+        $this->getClient()->resetApplication();
         $this->configureClient($this->config);
         $this->yiiLogger->getAndClearLog();
-        $this->client->startApp($this->yiiLogger);
+        $this->getClient()->startApp($this->yiiLogger);
     }
 
     /**
@@ -248,7 +250,7 @@ protected function onReconfigure()
      * Note this is done separately from the request cycle since someone might call
      * `Url::to` before doing a request, which would instantiate the request component with incorrect server params.
      */
-    private function initServerGlobal()
+    private function initServerGlobal(): void
     {
 
         $entryUrl = $this->config['entryUrl'];
@@ -290,22 +292,22 @@ protected function validateConfig(): void
         }
     }
 
-    protected function configureClient(array $settings)
+    protected function configureClient(array $settings): void
     {
         $settings['configFile'] = codecept_absolute_path($settings['configFile']);
 
         foreach ($settings as $key => $value) {
             if (property_exists($this->client, $key)) {
-                $this->client->$key = $value;
+                $this->getClient()->$key = $value;
             }
         }
-        $this->client->resetApplication();
+        $this->getClient()->resetApplication();
     }
 
     /**
      * Instantiates the client based on module configuration
      */
-    protected function recreateClient()
+    protected function recreateClient(): void
     {
         $entryUrl = $this->config['entryUrl'];
         $entryFile = $this->config['entryScript'] ?: basename($entryUrl);
@@ -322,13 +324,13 @@ protected function recreateClient()
         $this->configureClient($this->config);
     }
 
-    public function _before(TestInterface $test)
+    public function _before(TestInterface $test): void
     {
         $this->recreateClient();
         $this->yiiLogger = new Yii2Connector\Logger();
-        $this->client->startApp($this->yiiLogger);
+        $this->getClient()->startApp($this->yiiLogger);
 
-        $this->connectionWatcher = new Yii2Connector\ConnectionWatcher();
+        $this->connectionWatcher = new ConnectionWatcher();
         $this->connectionWatcher->start();
 
         // load fixtures before db transaction
@@ -346,16 +348,14 @@ public function _before(TestInterface $test)
 
     /**
      * load fixtures before db transaction
-     *
-     * @param mixed $test instance of test class
      */
-    private function loadFixtures($test)
+    private function loadFixtures(object $test): void
     {
         $this->debugSection('Fixtures', 'Loading fixtures');
         if (empty($this->loadedFixtures)
             && method_exists($test, $this->_getConfig('fixturesMethod'))
         ) {
-            $connectionWatcher = new Yii2Connector\ConnectionWatcher();
+            $connectionWatcher = new ConnectionWatcher();
             $connectionWatcher->start();
             $this->haveFixtures(call_user_func([$test, $this->_getConfig('fixturesMethod')]));
             $connectionWatcher->stop();
@@ -364,7 +364,7 @@ private function loadFixtures($test)
         $this->debugSection('Fixtures', 'Done');
     }
 
-    public function _after(TestInterface $test)
+    public function _after(TestInterface $test): void
     {
         $_SESSION = [];
         $_FILES = [];
@@ -382,9 +382,7 @@ public function _after(TestInterface $test)
             $this->loadedFixtures = [];
         }
 
-        if ($this->client !== null) {
-            $this->client->resetApplication();
-        }
+        $this->getClient()?->resetApplication();
 
         if (isset($this->connectionWatcher)) {
             $this->connectionWatcher->stop();
@@ -395,24 +393,25 @@ public function _after(TestInterface $test)
         parent::_after($test);
     }
 
-    public function _failed(TestInterface $test, $fail)
+    public function _failed(TestInterface $test, $fail): void
     {
-        if ($this->yiiLogger && $log = $this->yiiLogger->getAndClearLog()) {
+        $log = $this->yiiLogger->getAndClearLog();
+        if ($log !== '') {
             $test->getMetadata()->addReport('yii-log', $log);
         }
 
         parent::_failed($test, $fail);
     }
 
-    protected function startTransactions()
+    protected function startTransactions(): void
     {
         if ($this->config['transaction']) {
-            $this->transactionForcer = new Yii2Connector\TransactionForcer($this->config['ignoreCollidingDSN']);
+            $this->transactionForcer = new TransactionForcer($this->config['ignoreCollidingDSN']);
             $this->transactionForcer->start();
         }
     }
 
-    protected function rollbackTransactions()
+    protected function rollbackTransactions(): void
     {
         if (isset($this->transactionForcer)) {
             $this->transactionForcer->rollbackAll();
@@ -441,13 +440,12 @@ public function _parts(): array
      * ```
      * Requires the `user` component to be enabled and configured.
      *
-     * @param $user
      * @throws \Codeception\Exception\ModuleException
      */
-    public function amLoggedInAs($user)
+    public function amLoggedInAs(int|string|IdentityInterface $user): void
     {
         try {
-            $this->client->findAndLoginUser($user);
+            $this->getClient()?->findAndLoginUser($user);
         } catch (ConfigurationException $e) {
             throw new ModuleException($this, $e->getMessage());
         } catch (\RuntimeException $e) {
@@ -491,7 +489,7 @@ public function amLoggedInAs($user)
      * @param $fixtures
      * @part fixtures
      */
-    public function haveFixtures($fixtures)
+    public function haveFixtures($fixtures): void
     {
         if (empty($fixtures)) {
             return;
@@ -571,15 +569,15 @@ public function grabFixture($name, $index = null)
      * $user_id = $I->haveRecord('app\models\User', array('name' => 'Davert'));
      * ?>
      * ```
-     *
-     * @param $model
-     * @param array $attributes
+     * @template T of \yii\db\ActiveRecord
+     * @param class-string<T> $model
+     * @param array<string, mixed> $attributes
      * @return mixed
      * @part orm
      */
-    public function haveRecord($model, $attributes = [])
+    public function haveRecord(string $model, $attributes = []): mixed
     {
-        /** @var $record \yii\db\ActiveRecord  * */
+        /** @var T $record   **/
         $record = \Yii::createObject($model);
         $record->setAttributes($attributes, false);
         $res = $record->save(false);
@@ -596,8 +594,8 @@ public function haveRecord($model, $attributes = [])
      * $I->seeRecord('app\models\User', array('name' => 'davert'));
      * ```
      *
-     * @param $model
-     * @param array $attributes
+     * @param class-string<\yii\db\ActiveRecord> $model
+     * @param array<string, mixed> $attributes
      * @part orm
      */
     public function seeRecord(string $model, array $attributes = []): void
@@ -616,8 +614,8 @@ public function seeRecord(string $model, array $attributes = []): void
      * $I->dontSeeRecord('app\models\User', array('name' => 'davert'));
      * ```
      *
-     * @param $model
-     * @param array $attributes
+     * @param class-string<\yii\db\ActiveRecord> $model
+     * @param array<string, mixed> $attributes
      * @part orm
      */
     public function dontSeeRecord(string $model, array $attributes = []): void
@@ -636,35 +634,34 @@ public function dontSeeRecord(string $model, array $attributes = []): void
      * $category = $I->grabRecord('app\models\User', array('name' => 'davert'));
      * ```
      *
-     * @param $model
-     * @param array $attributes
-     * @return mixed
+     * @param class-string<\yii\db\ActiveRecord> $model
+     * @param array<string, mixed> $attributes
      * @part orm
      */
-    public function grabRecord(string $model, array $attributes = []): mixed
+    public function grabRecord(string $model, array $attributes = []): \yii\db\ActiveRecord|null|array
     {
         return $this->findRecord($model, $attributes);
     }
 
     /**
-     * @param string $model Class name
-     * @param array $attributes
-     * @return mixed
+     * @param class-string<\yii\db\ActiveRecord> $model Class name
+     * @param array<string, mixed> $attributes
      */
-    protected function findRecord(string $model, array $attributes = []): mixed
+    protected function findRecord(string $model, array $attributes = []): \yii\db\ActiveRecord | null | array
     {
         if (!class_exists($model)) {
             throw new \RuntimeException("Class $model does not exist");
         }
         $rc = new \ReflectionClass($model);
         if ($rc->hasMethod('find')
+            /** @phpstan-ignore-next-line */
             && ($findMethod = $rc->getMethod('find'))
             && $findMethod->isStatic()
             && $findMethod->isPublic()
             && $findMethod->getNumberOfRequiredParameters() === 0
         ) {
             $activeQuery = $findMethod->invoke(null);
-            if ($activeQuery instanceof QueryInterface) {
+            if ($activeQuery instanceof ActiveQueryInterface) {
                 return $activeQuery->andWhere($attributes)->one();
             }
 
@@ -693,41 +690,6 @@ public function amOnRoute(string $route, array $params = []): void
         $this->amOnPage(Url::to($params));
     }
 
-    /**
-     * Opens the page for the given relative URI or route.
-     *
-     * ``` php
-     * <?php
-     * // opens front page
-     * $I->amOnPage('/');
-     * // opens /register page
-     * $I->amOnPage('/register');
-     * ```
-     *
-     * @param string $page the page URI
-     */
-    public function amOnPage(string $page): void
-    {
-        parent::amOnPage($page);
-    }
-
-    /**
-     * To support to use the behavior of urlManager component
-     * for the methods like this: amOnPage(), sendAjaxRequest() and etc.
-     * @param $method
-     * @param $uri
-     * @param array $parameters
-     * @param array $files
-     * @param array $server
-     * @param null $content
-     * @param bool $changeHistory
-     * @return mixed
-     */
-    protected function clientRequest(string $method, string $uri,  array $parameters = [],  array $files = [], array $server = [], string $content = null, bool $changeHistory = true): SymfonyCrawler
-    {
-        return parent::clientRequest($method, $this->client->createUrl($uri), $parameters, $files, $server, $content, $changeHistory);
-    }
-
     /**
      * Gets a component from the Yii container. Throws an exception if the
      * component is not available
@@ -737,15 +699,13 @@ protected function clientRequest(string $method, string $uri,  array $parameters
      * $mailer = $I->grabComponent('mailer');
      * ```
      *
-     * @param $component
-     * @return mixed
      * @throws \Codeception\Exception\ModuleException
      * @deprecated in your tests you can use \Yii::$app directly.
      */
-    public function grabComponent(mixed $component)
+    public function grabComponent(string $component): null|object
     {
         try {
-            return $this->client->getComponent($component);
+            return $this->getClient()->getComponent($component);
         } catch (ConfigurationException $e) {
             throw new ModuleException($this, $e->getMessage());
         }
@@ -805,7 +765,7 @@ public function dontSeeEmailIsSent(): void
     public function grabSentEmails(): array
     {
         try {
-            return $this->client->getEmails();
+            return $this->getClient()->getEmails();
         } catch (ConfigurationException $e) {
             throw new ModuleException($this, $e->getMessage());
         }
@@ -838,7 +798,7 @@ public function grabLastSentEmail(): object
      */
     public function getInternalDomains(): array
     {
-        return $this->client->getInternalDomains();
+        return $this->getClient()->getInternalDomains();
     }
 
     private function defineConstants(): void
@@ -856,7 +816,7 @@ private function defineConstants(): void
      */
     public function setCookie($name, $val, $params = [])
     {
-        parent::setCookie($name, $this->client->hashCookieData($name, $val), $params);
+        parent::setCookie($name, $this->getClient()->hashCookieData($name, $val), $params);
     }
 
     /**
@@ -866,8 +826,8 @@ public function setCookie($name, $val, $params = [])
      */
     public function createAndSetCsrfCookie(string $val): array
     {
-        $masked = $this->client->maskToken($val);
-        $name = $this->client->getCsrfParamName();
+        $masked = (new Security())->maskToken($val);
+        $name = $this->getClient()->getCsrfParamName();
         $this->setCookie($name, $val);
         return [$name, $masked];
     }
@@ -885,7 +845,7 @@ public function _afterSuite(): void
      */
     public function _initializeSession(): void
     {
-        $this->client->removeContext();
+        $this->getClient()->restart();
         $this->headers = [];
         $_SESSION = [];
         $_COOKIE = [];
@@ -893,15 +853,15 @@ public function _initializeSession(): void
 
     /**
      * Return the session content for future restoring. Implements MultiSession.
-     * @return array backup data
+     * @return array<string, mixed> backup data
      */
     public function _backupSession(): array
     {
-        if (isset(Yii::$app) && Yii::$app->has('session', true) && Yii::$app->session->useCustomStorage) {
+        if (Yii::$app instanceof Application && Yii::$app->has('session', true) && Yii::$app->session->useCustomStorage) {
             throw new ModuleException($this, "Yii2 MultiSession only supports the default session backend.");
         }
         return [
-            'clientContext' => $this->client->getContext(),
+            'clientContext' => $this->getClient()->getContext(),
             'headers' => $this->headers,
             'cookie' => isset($_COOKIE) ? $_COOKIE : [],
             'session' => isset($_SESSION) ? $_SESSION : [],
@@ -910,20 +870,21 @@ public function _backupSession(): array
 
     /**
      * Restore a session. Implements MultiSession.
-     * @param array output of _backupSession()
+     * @param array<mixed> $session output of _backupSession()
      */
     public function _loadSession($session): void
     {
-        $this->client->setContext($session['clientContext']);
+        $this->getClient()->setContext($session['clientContext']);
         $this->headers = $session['headers'];
         $_SESSION = $session['session'];
         $_COOKIE = $session['cookie'];
 
         // reset Yii::$app->user
         if (isset(Yii::$app)) {
-            $definitions = Yii::$app->getComponents(true);
-            if (Yii::$app->has('user', true)) {
-                Yii::$app->set('user', $definitions['user']);
+            $app = Yii::$app;
+            $definitions = $app->getComponents(true);
+            if ($app->has('user', true)) {
+                $app->set('user', $definitions['user']);
             }
         }
     }
diff --git a/tests/Yii.stub b/tests/Yii.stub
new file mode 100644
index 0000000..2a715d2
--- /dev/null
+++ b/tests/Yii.stub
@@ -0,0 +1,38 @@
+<?php declare(strict_types=1);
+
+
+
+namespace yii {
+    use \yii\base\Application;
+
+    class BaseYii
+    {
+        /**
+         * @var Application|null $app
+         */
+        public static $app;
+    }
+}
+
+namespace yii\base {
+
+    class Application {}
+}
+
+namespace yii\web {
+    class Response {
+        /**
+         * @var array{0: resource, 1:int, 2:int}|callable|resource|null
+         */
+        public $stream;
+    }
+
+    class Request {
+        /**
+         * @param string|null $url
+         * @return void
+         */
+        public function setBaseUrl($url) {}
+    }
+
+}