diff --git a/LICENSE.md b/LICENSE.md
index bc5674fe4..6a920d605 100644
--- a/LICENSE.md
+++ b/LICENSE.md
@@ -1,17 +1,17 @@
-Copyright © 2008 by Yii Software (https://www.yiiframework.com/)
+Copyright © 2008 by Yii Software (<https://www.yiiframework.com/>)
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions
 are met:
 
- * Redistributions of source code must retain the above copyright
+* Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.
- * Redistributions in binary form must reproduce the above copyright
+* Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in
    the documentation and/or other materials provided with the
    distribution.
- * Neither the name of Yii Software nor the names of its
+* Neither the name of Yii Software nor the names of its
    contributors may be used to endorse or promote products derived
    from this software without specific prior written permission.
 
diff --git a/README.md b/README.md
index a58e3f1f1..faec76866 100644
--- a/README.md
+++ b/README.md
@@ -19,7 +19,7 @@ It is used in [Yii Framework] but is supposed to be usable separately.
 [![static analysis](https://github.com/yiisoft/active-record/actions/workflows/static.yml/badge.svg?branch=dev)](https://github.com/yiisoft/active-record/actions/workflows/static.yml)
 [![type-coverage](https://shepherd.dev/github/yiisoft/active-record/coverage.svg)](https://shepherd.dev/github/yiisoft/active-record)
 
-## Support databases:
+## Support databases
 
 |Packages|  PHP | Versions            |  CI-Actions
 |:------:|:----:|:------------------------:|:-----------:|
@@ -29,11 +29,15 @@ It is used in [Yii Framework] but is supposed to be usable separately.
 |[[db-pgsql]](https://github.com/yiisoft/db-pgsql)|**7.4 - 8.0**| **9.0 - 15.0**|[![Build status](https://github.com/yiisoft/db-pgsql/workflows/build/badge.svg)](https://github.com/yiisoft/db-pgsql/actions?query=workflow%3Abuild) [![Mutation testing badge](https://img.shields.io/endpoint?style=flat&url=https%3A%2F%2Fbadge-api.stryker-mutator.io%2Fgithub.com%2Fyiisoft%2Fdb-pgsql%2Fmaster)](https://dashboard.stryker-mutator.io/reports/github.com/yiisoft/db-pgsql/master) [![codecov](https://codecov.io/gh/yiisoft/db-pgsql/branch/master/graph/badge.svg?token=3FGN91IVZA)](https://codecov.io/gh/yiisoft/db-pgsql)|
 |[[db-sqlite]](https://github.com/yiisoft/db-sqlite)|**7.4 - 8.0**| **3:latest**|[![Build status](https://github.com/yiisoft/db-sqlite/workflows/build/badge.svg)](https://github.com/yiisoft/db-sqlite/actions?query=workflow%3Abuild) [![Mutation testing badge](https://img.shields.io/endpoint?style=flat&url=https%3A%2F%2Fbadge-api.stryker-mutator.io%2Fgithub.com%2Fyiisoft%2Fdb-sqlite%2Fmaster)](https://dashboard.stryker-mutator.io/reports/github.com/yiisoft/db-sqlite/master) [![codecov](https://codecov.io/gh/yiisoft/db-sqlite/branch/master/graph/badge.svg?token=YXUHCPPITH)](https://codecov.io/gh/yiisoft/db-sqlite)|
 
+## Requirements
+
+- PHP 8.1 or higher.
+
 ## Installation
 
 The package could be installed via composer:
 
-```php
+```shell
 composer require yiisoft/active-record
 ```
 
@@ -41,18 +45,15 @@ composer require yiisoft/active-record
 
 Example:
 
-```php
+```shell
 composer require yiisoft/db-sqlite
 ```
 
 ## Config container interface class
 
 web.php:
-```php
-<?php
-
-declare(strict_types=1);
 
+```php
 use Yiisoft\Db\Connection\ConnectionInterface;
 use Yiisoft\Db\Sqlite\Connection;
 use Yiisoft\Db\Sqlite\Driver;
@@ -71,11 +72,8 @@ return [
 ```
 
 params.php
-```php
-<?php
-
-declare(strict_types=1);
 
+```php
 return [
     'yiisoft/db-sqlite' => [
         'dsn' => 'sqlite:' . dirname(__DIR__) . '/runtime/yiitest.sq3',
@@ -86,12 +84,6 @@ return [
 ## Defined your active record class
 
 ```php
-<?php
-
-declare(strict_types=1);
-
-namespace App\Entity;
-
 use Yiisoft\ActiveRecord\ActiveRecord;
 
 /**
@@ -114,12 +106,6 @@ final class User extends ActiveRecord
 ## Usage in controler with DI container autowiring
 
 ```php
-<?php
-
-declare(strict_types=1);
-
-namespace App\Action;
-
 use App\Entity\User;
 use Psr\Http\Message\ResponseInterface;
 
@@ -139,12 +125,6 @@ final class Register
 ## Usage in controler with Active Record factory
 
 ```php
-<?php
-
-declare(strict_types=1);
-
-namespace App\Action;
-
 use App\Entity\User;
 use Psr\Http\Message\ResponseInterface;
 use Yiisoft\ActiveRecord\ActiveRecordFactory;
@@ -164,20 +144,20 @@ final class Register
 }
 ```
 
-## Support
+## Documentation
 
-If you need help or have a question, the [Yii Forum](https://forum.yiiframework.com/c/yii-3-0/db/68) is a good place for that.
-You may also check out other [Yii Community Resources](https://www.yiiframework.com/community).
+- [Internals](docs/internals.md)
 
-## Testing
+## Support
 
-[Check the testing instructions](/docs/en/testing.md) to learn about testing.
+If you need help or have a question, the [Yii Forum](https://forum.yiiframework.com/c/yii-3-0/63) is a good place for that.
+You may also check out other [Yii Community Resources](https://www.yiiframework.com/community).
 
-### Support the project
+## Support the project
 
 [![Open Collective](https://img.shields.io/badge/Open%20Collective-sponsor-7eadf1?logo=open%20collective&logoColor=7eadf1&labelColor=555555)](https://opencollective.com/yiisoft)
 
-### Follow updates
+## Follow updates
 
 [![Official website](https://img.shields.io/badge/Powered_by-Yii_Framework-green.svg?style=flat)](https://www.yiiframework.com/)
 [![Twitter](https://img.shields.io/badge/twitter-follow-1DA1F2?logo=twitter&logoColor=1DA1F2&labelColor=555555?style=flat)](https://twitter.com/yiiframework)
diff --git a/docs/en/testing.md b/docs/internals.md
similarity index 84%
rename from docs/en/testing.md
rename to docs/internals.md
index 602bc8012..f21f6b2e1 100644
--- a/docs/en/testing.md
+++ b/docs/internals.md
@@ -1,4 +1,4 @@
-# Testing
+# Internals
 
 This package can be tested globally or individually for each DBMS.
 
@@ -30,10 +30,6 @@ To run Docker containers you can use the following command:
 docker compose up -d
 ```
 
-## Unit testing
-
-The package is tested with [PHPUnit](https://phpunit.de/).
-
 ### Global testing
 
 The following steps are required to run tests.
@@ -69,12 +65,30 @@ vendor/bin/phpunit --testsuite=Pgsql
 ```
 
 Suites available:
+
 - Mssql
 - Mysql
 - Oracle
 - Pgsql
 - Sqlite
 
+## Unit testing
+
+The package is tested with [PHPUnit](https://phpunit.de/). To run tests:
+
+```shell
+./vendor/bin/phpunit
+```
+
+## Mutation testing
+
+The package tests are checked with [Infection](https://infection.github.io/) mutation framework with
+[Infection Static Analysis Plugin](https://github.com/Roave/infection-static-analysis-plugin). To run it:
+
+```shell
+./vendor/bin/roave-infection-static-analysis-plugin
+```
+
 ## Static analysis
 
 The code is statically analyzed with [Psalm](https://psalm.dev/). To run static analysis:
@@ -85,7 +99,8 @@ The code is statically analyzed with [Psalm](https://psalm.dev/). To run static
 
 ## Rector
 
-Use [Rector](https://github.com/rectorphp/rector) to make codebase follow some specific rules or use either newest or any specific version of PHP: 
+Use [Rector](https://github.com/rectorphp/rector) to make codebase follow some specific rules or
+use either newest or any specific version of PHP:
 
 ```shell
 ./vendor/bin/rector
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index b92f0e1b3..77711bcfa 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" backupGlobals="false" colors="true" bootstrap="vendor/autoload.php" failOnRisky="true" failOnWarning="true" executionOrder="default" resolveDependencies="true" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.1/phpunit.xsd">
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" backupGlobals="false" colors="true" bootstrap="vendor/autoload.php" failOnRisky="true" failOnWarning="true" executionOrder="default" resolveDependencies="true" xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/10.1/phpunit.xsd">
   <coverage/>
   <php>
     <ini name="error_reporting" value="-1"/>