diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
index 9e3bbfd..8926eda 100644
--- a/.github/workflows/continuous-integration.yml
+++ b/.github/workflows/continuous-integration.yml
@@ -13,8 +13,6 @@ jobs:
     strategy:
       matrix:
         php-version:
-          - "8.1"
-          - "8.2"
           - "8.3"
           - "8.4"
           - "8.5"
@@ -50,7 +48,7 @@ jobs:
       - name: Install PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: 8.1
+          php-version: 8.3
           coverage: pcov
 
       - name: Install Dependencies
@@ -74,7 +72,7 @@ jobs:
       - name: Install PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: 8.1
+          php-version: 8.3
           coverage: none
 
       - name: Install dependencies
diff --git a/README.md b/README.md
index 0fffff0..f455d23 100644
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@ using [Composer](http://getcomposer.org).
 composer require respect/stringifier
 ```
 
-This library requires PHP >= 8.1.
+This library requires PHP >= 8.3.
 
 ## Usage
 
@@ -190,4 +190,4 @@ echo $stringify->value(new class {
     }
 });
 // Hello, world!
-```
\ No newline at end of file
+```
diff --git a/composer.json b/composer.json
index 5d06640..fc4d03f 100644
--- a/composer.json
+++ b/composer.json
@@ -11,17 +11,16 @@
         }
     ],
     "require": {
-        "php": "^8.1"
+        "php": "^8.3"
     },
     "require-dev": {
         "malukenho/docheader": "^0.1.7",
-        "phpstan/phpstan": "^1.10",
-        "phpstan/phpstan-deprecation-rules": "^1.1",
-        "phpstan/phpstan-phpunit": "^1.3",
-        "phpstan/phpstan-strict-rules": "^1.5",
-        "phpunit/phpunit": "^10.0",
-        "respect/coding-standard": "^4.0",
-        "squizlabs/php_codesniffer": "^3.7"
+        "phpstan/phpstan": "^2.1",
+        "phpstan/phpstan-deprecation-rules": "^2.0",
+        "phpstan/phpstan-phpunit": "^2.0",
+        "phpstan/phpstan-strict-rules": "^2.0",
+        "phpunit/phpunit": "^12.5",
+        "respect/coding-standard": "^5.0"
     },
     "autoload": {
         "psr-4": {
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index 5f374f3..1e228c6 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -17,4 +17,19 @@
     <rule ref="PSR1.Classes.ClassDeclaration.MissingNamespace">
         <exclude-pattern>tests/fixtures/</exclude-pattern>
     </rule>
+    <rule ref="Squiz.Arrays.ArrayDeclaration.ValueNoNewline">
+        <exclude-pattern>tests/unit/Stringifiers/CallableStringifierTest.php</exclude-pattern>
+    </rule>
+    <rule ref="Squiz.Functions.GlobalFunction">
+        <exclude-pattern>tests/integration/lib/helpers.php</exclude-pattern>
+    </rule>
+    <rule ref="Generic.Files.InlineHTML.Found">
+        <exclude-pattern>tests/integration/</exclude-pattern>
+    </rule>
+    <rule ref="PSR12.Files.FileHeader.HeaderPosition">
+        <exclude-pattern>tests/integration/</exclude-pattern>
+    </rule>
+    <rule ref="Generic.PHP.CharacterBeforePHPOpeningTag.Found">
+        <exclude-pattern>tests/integration/</exclude-pattern>
+    </rule>
 </ruleset>
diff --git a/src/Helpers/ObjectHelper.php b/src/Helpers/ObjectHelper.php
index 47555c8..c3154f6 100644
--- a/src/Helpers/ObjectHelper.php
+++ b/src/Helpers/ObjectHelper.php
@@ -18,7 +18,7 @@
 
 trait ObjectHelper
 {
-    private function format(object $object, ?string ...$pieces): string
+    private function format(object $object, string|null ...$pieces): string
     {
         $filteredPieces = array_filter($pieces);
         if (count($filteredPieces) === 0) {
diff --git a/src/Quoters/StandardQuoter.php b/src/Quoters/StandardQuoter.php
index 59c4cd4..44e6ccc 100644
--- a/src/Quoters/StandardQuoter.php
+++ b/src/Quoters/StandardQuoter.php
@@ -20,9 +20,9 @@
 
 final class StandardQuoter implements Quoter
 {
-    private const OBJECT_PLACEHOLDER = ' ... }';
-    private const ARRAY_PLACEHOLDER = ' ... ]';
-    private const GENERIC_PLACEHOLDER = ' ...';
+    private const string OBJECT_PLACEHOLDER = ' ... }';
+    private const string ARRAY_PLACEHOLDER = ' ... ]';
+    private const string GENERIC_PLACEHOLDER = ' ...';
 
     public function __construct(private readonly int $maximumLength)
     {
diff --git a/src/Stringifier.php b/src/Stringifier.php
index c8d423d..7b066a3 100644
--- a/src/Stringifier.php
+++ b/src/Stringifier.php
@@ -12,5 +12,5 @@
 
 interface Stringifier
 {
-    public function stringify(mixed $raw, int $depth): ?string;
+    public function stringify(mixed $raw, int $depth): string|null;
 }
diff --git a/src/Stringifiers/ArrayObjectStringifier.php b/src/Stringifiers/ArrayObjectStringifier.php
index 314742a..bfec6bd 100644
--- a/src/Stringifiers/ArrayObjectStringifier.php
+++ b/src/Stringifiers/ArrayObjectStringifier.php
@@ -21,11 +21,11 @@ final class ArrayObjectStringifier implements Stringifier
 
     public function __construct(
         private readonly Stringifier $stringifier,
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!$raw instanceof ArrayObject) {
             return null;
@@ -33,7 +33,7 @@ public function stringify(mixed $raw, int $depth): ?string
 
         return $this->quoter->quote(
             $this->format($raw, 'getArrayCopy() =>', $this->stringifier->stringify($raw->getArrayCopy(), $depth + 1)),
-            $depth
+            $depth,
         );
     }
 }
diff --git a/src/Stringifiers/ArrayStringifier.php b/src/Stringifiers/ArrayStringifier.php
index 1d009b9..9c85f52 100644
--- a/src/Stringifiers/ArrayStringifier.php
+++ b/src/Stringifiers/ArrayStringifier.php
@@ -22,17 +22,17 @@
 
 final class ArrayStringifier implements Stringifier
 {
-    private const LIMIT_EXCEEDED_PLACEHOLDER = '...';
+    private const string LIMIT_EXCEEDED_PLACEHOLDER = '...';
 
     public function __construct(
         private readonly Stringifier $stringifier,
         private readonly Quoter $quoter,
         private readonly int $maximumDepth,
-        private readonly int $maximumNumberOfItems
+        private readonly int $maximumNumberOfItems,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!is_array($raw)) {
             return null;
@@ -66,7 +66,7 @@ public function stringify(mixed $raw, int $depth): ?string
         return $this->quoter->quote(sprintf('[%s]', implode(', ', $items)), $depth);
     }
 
-    private function stringifyKeyValue(mixed $value, int $depth): ?string
+    private function stringifyKeyValue(mixed $value, int $depth): string|null
     {
         if (is_array($value)) {
             return $this->stringify($value, $depth);
@@ -75,9 +75,7 @@ private function stringifyKeyValue(mixed $value, int $depth): ?string
         return $this->stringifier->stringify($value, $depth);
     }
 
-    /**
-     * @param mixed[] $array
-     */
+    /** @param mixed[] $array */
     private function isSequential(array $array): bool
     {
         return array_keys($array) === range(0, count($array) - 1);
diff --git a/src/Stringifiers/BoolStringifier.php b/src/Stringifiers/BoolStringifier.php
index 205209b..323920d 100644
--- a/src/Stringifiers/BoolStringifier.php
+++ b/src/Stringifiers/BoolStringifier.php
@@ -18,11 +18,11 @@
 final class BoolStringifier implements Stringifier
 {
     public function __construct(
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!is_bool($raw)) {
             return null;
diff --git a/src/Stringifiers/CallableStringifier.php b/src/Stringifiers/CallableStringifier.php
index acf6d10..6158199 100644
--- a/src/Stringifiers/CallableStringifier.php
+++ b/src/Stringifiers/CallableStringifier.php
@@ -47,7 +47,7 @@ public function __construct(
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!is_callable($raw)) {
             return null;
@@ -61,16 +61,15 @@ public function stringify(mixed $raw, int $depth): ?string
             return $this->buildMethod(new ReflectionMethod($raw, '__invoke'), $raw, $depth);
         }
 
-        if (is_array($raw) && is_object($raw[0])) {
+        if (is_array($raw) && is_object($raw[0]) && is_string($raw[1])) {
             return $this->buildMethod(new ReflectionMethod($raw[0], $raw[1]), $raw[0], $depth);
         }
 
-        if (is_array($raw) && is_string($raw[0])) {
+        if (is_array($raw) && is_string($raw[0]) && is_string($raw[1])) {
             return $this->buildStaticMethod(new ReflectionMethod($raw[0], $raw[1]), $depth);
         }
 
-        /** @var callable-string $raw */
-        if (str_contains($raw, ':')) {
+        if (is_string($raw) && str_contains($raw, ':')) {
             /** @var class-string $class */
             $class = (string) strstr($raw, ':', true);
             $method = substr((string) strrchr($raw, ':'), 1);
@@ -78,10 +77,14 @@ public function stringify(mixed $raw, int $depth): ?string
             return $this->buildStaticMethod(new ReflectionMethod($class, $method), $depth);
         }
 
+        if (!is_string($raw)) {
+            return null;
+        }
+
         return $this->buildFunction(new ReflectionFunction($raw), $depth);
     }
 
-    public function buildFunction(ReflectionFunction $raw, int $depth): ?string
+    public function buildFunction(ReflectionFunction $raw, int $depth): string
     {
         return $this->quoter->quote($this->buildSignature($raw, $depth), $depth);
     }
@@ -90,7 +93,7 @@ private function buildMethod(ReflectionMethod $reflection, object $object, int $
     {
         return $this->quoter->quote(
             sprintf('%s->%s', $this->getName($object), $this->buildSignature($reflection, $depth)),
-            $depth
+            $depth,
         );
     }
 
@@ -98,7 +101,7 @@ private function buildStaticMethod(ReflectionMethod $reflection, int $depth): st
     {
         return $this->quoter->quote(
             sprintf('%s::%s', $reflection->class, $this->buildSignature($reflection, $depth)),
-            $depth
+            $depth,
         );
     }
 
@@ -112,10 +115,10 @@ private function buildSignature(ReflectionFunctionAbstract $function, int $depth
                 array_map(
                     fn(ReflectionParameter $parameter): string => $this->buildParameter(
                         $parameter,
-                        $depth + 1
+                        $depth + 1,
                     ),
-                    $function->getParameters()
-                )
+                    $function->getParameters(),
+                ),
             ),
         );
 
@@ -125,7 +128,7 @@ private function buildSignature(ReflectionFunctionAbstract $function, int $depth
                 ' use ($%s)',
                 implode(
                     ', $',
-                    array_keys($closureUsedVariables)
+                    array_keys($closureUsedVariables),
                 ),
             );
         }
@@ -160,7 +163,7 @@ private function buildParameter(ReflectionParameter $reflectionParameter, int $d
         return $parameter;
     }
 
-    private function buildValue(ReflectionParameter $reflectionParameter, int $depth): ?string
+    private function buildValue(ReflectionParameter $reflectionParameter, int $depth): string|null
     {
         if (!$reflectionParameter->isDefaultValueAvailable()) {
             return $this->stringifier->stringify(null, $depth);
@@ -178,19 +181,26 @@ private function buildType(ReflectionType $raw, int $depth): string
         if ($raw instanceof ReflectionUnionType) {
             return implode(
                 '|',
-                array_map(fn(ReflectionType $type) => $this->buildType($type, $depth), $raw->getTypes())
+                array_map(fn(ReflectionType $type) => $this->buildType($type, $depth), $raw->getTypes()),
             );
         }
 
         if ($raw instanceof ReflectionIntersectionType) {
             return implode(
                 '&',
-                array_map(fn(ReflectionType $type) => $this->buildType($type, $depth), $raw->getTypes())
+                array_map(fn(ReflectionType $type) => $this->buildType($type, $depth), $raw->getTypes()),
             );
         }
 
-        /** @var ReflectionNamedType $raw */
+        if ($raw instanceof ReflectionNamedType) {
+            $type = $raw->getName();
+            if ($raw->allowsNull()) {
+                $type = sprintf('?%s', $type);
+            }
+
+            return $type;
+        }
 
-        return ($raw->allowsNull() ? '?' : '') . $raw->getName();
+        return '';
     }
 }
diff --git a/src/Stringifiers/CompositeStringifier.php b/src/Stringifiers/CompositeStringifier.php
index 4341845..21926f9 100644
--- a/src/Stringifiers/CompositeStringifier.php
+++ b/src/Stringifiers/CompositeStringifier.php
@@ -18,14 +18,12 @@
 
 final class CompositeStringifier implements Stringifier
 {
-    private const MAXIMUM_DEPTH = 3;
-    private const MAXIMUM_NUMBER_OF_ITEMS = 5;
-    private const MAXIMUM_NUMBER_OF_PROPERTIES = self::MAXIMUM_NUMBER_OF_ITEMS;
-    private const MAXIMUM_LENGTH = 120;
+    private const int MAXIMUM_DEPTH = 3;
+    private const int MAXIMUM_NUMBER_OF_ITEMS = 5;
+    private const int MAXIMUM_NUMBER_OF_PROPERTIES = self::MAXIMUM_NUMBER_OF_ITEMS;
+    private const int MAXIMUM_LENGTH = 120;
 
-    /**
-     * @var Stringifier[]
-     */
+    /** @var Stringifier[] */
     private array $stringifiers = [];
 
     public function __construct(Stringifier ...$stringifiers)
@@ -52,15 +50,15 @@ public static function createDefault(): self
                 $quoter,
                 self::MAXIMUM_DEPTH,
                 self::MAXIMUM_NUMBER_OF_ITEMS,
-            )
+            ),
         );
         $stringifier->prependStringifier(
             new ObjectStringifier(
                 $stringifier,
                 $quoter,
                 self::MAXIMUM_DEPTH,
-                self::MAXIMUM_NUMBER_OF_PROPERTIES
-            )
+                self::MAXIMUM_NUMBER_OF_PROPERTIES,
+            ),
         );
         $stringifier->prependStringifier($callableStringifier = new CallableStringifier($stringifier, $quoter));
         $stringifier->prependStringifier(new FiberObjectStringifier($callableStringifier, $quoter));
@@ -81,7 +79,7 @@ public function prependStringifier(Stringifier $stringifier): void
          array_unshift($this->stringifiers, $stringifier);
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         foreach ($this->stringifiers as $stringifier) {
             $string = $stringifier->stringify($raw, $depth);
diff --git a/src/Stringifiers/DateTimeStringifier.php b/src/Stringifiers/DateTimeStringifier.php
index 6c6c9d8..926d088 100644
--- a/src/Stringifiers/DateTimeStringifier.php
+++ b/src/Stringifiers/DateTimeStringifier.php
@@ -21,11 +21,11 @@ final class DateTimeStringifier implements Stringifier
 
     public function __construct(
         private readonly Quoter $quoter,
-        private readonly string $format
+        private readonly string $format,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!$raw instanceof DateTimeInterface) {
             return null;
diff --git a/src/Stringifiers/DeclaredStringifier.php b/src/Stringifiers/DeclaredStringifier.php
index 065689a..39b59c9 100644
--- a/src/Stringifiers/DeclaredStringifier.php
+++ b/src/Stringifiers/DeclaredStringifier.php
@@ -22,11 +22,11 @@
 final class DeclaredStringifier implements Stringifier
 {
     public function __construct(
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!is_string($raw) || $this->isNotDeclared($raw)) {
             return null;
diff --git a/src/Stringifiers/EnumerationStringifier.php b/src/Stringifiers/EnumerationStringifier.php
index 5a3f9fa..f56c63a 100644
--- a/src/Stringifiers/EnumerationStringifier.php
+++ b/src/Stringifiers/EnumerationStringifier.php
@@ -19,11 +19,11 @@
 final class EnumerationStringifier implements Stringifier
 {
     public function __construct(
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!$raw instanceof UnitEnum) {
             return null;
diff --git a/src/Stringifiers/FiberObjectStringifier.php b/src/Stringifiers/FiberObjectStringifier.php
index 6aebd31..353396d 100644
--- a/src/Stringifiers/FiberObjectStringifier.php
+++ b/src/Stringifiers/FiberObjectStringifier.php
@@ -21,11 +21,11 @@ final class FiberObjectStringifier implements Stringifier
 {
     public function __construct(
         private readonly Stringifier $stringifier,
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!$raw instanceof Fiber) {
             return null;
@@ -34,9 +34,9 @@ public function stringify(mixed $raw, int $depth): ?string
         return $this->quoter->quote(
             sprintf(
                 'Fiber { %s }',
-                $this->stringifier->stringify((new ReflectionFiber($raw))->getCallable(), $depth + 1)
+                $this->stringifier->stringify((new ReflectionFiber($raw))->getCallable(), $depth + 1),
             ),
-            $depth
+            $depth,
         );
     }
 }
diff --git a/src/Stringifiers/InfiniteNumberStringifier.php b/src/Stringifiers/InfiniteNumberStringifier.php
index c485538..39ec918 100644
--- a/src/Stringifiers/InfiniteNumberStringifier.php
+++ b/src/Stringifiers/InfiniteNumberStringifier.php
@@ -19,11 +19,11 @@
 final class InfiniteNumberStringifier implements Stringifier
 {
     public function __construct(
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!is_float($raw)) {
             return null;
diff --git a/src/Stringifiers/IteratorObjectStringifier.php b/src/Stringifiers/IteratorObjectStringifier.php
index aa0ad5a..de578af 100644
--- a/src/Stringifiers/IteratorObjectStringifier.php
+++ b/src/Stringifiers/IteratorObjectStringifier.php
@@ -21,11 +21,11 @@ final class IteratorObjectStringifier implements Stringifier
 
     public function __construct(
         private readonly Stringifier $stringifier,
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!$raw instanceof Iterator) {
             return null;
@@ -37,7 +37,7 @@ public function stringify(mixed $raw, int $depth): ?string
 
         return $this->quoter->quote(
             $this->format($raw, 'current() =>', $this->stringifier->stringify($raw->current(), $depth + 1)),
-            $depth
+            $depth,
         );
     }
 }
diff --git a/src/Stringifiers/JsonEncodableStringifier.php b/src/Stringifiers/JsonEncodableStringifier.php
index e1a21ea..36e5c77 100644
--- a/src/Stringifiers/JsonEncodableStringifier.php
+++ b/src/Stringifiers/JsonEncodableStringifier.php
@@ -20,7 +20,7 @@
 
 final class JsonEncodableStringifier implements Stringifier
 {
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         $string = json_encode($raw, (JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES | JSON_PRESERVE_ZERO_FRACTION));
         if ($string === false) {
diff --git a/src/Stringifiers/JsonSerializableObjectStringifier.php b/src/Stringifiers/JsonSerializableObjectStringifier.php
index 2d8d077..a20eced 100644
--- a/src/Stringifiers/JsonSerializableObjectStringifier.php
+++ b/src/Stringifiers/JsonSerializableObjectStringifier.php
@@ -21,11 +21,11 @@ final class JsonSerializableObjectStringifier implements Stringifier
 
     public function __construct(
         private readonly Stringifier $stringifier,
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!$raw instanceof JsonSerializable) {
             return null;
@@ -33,7 +33,7 @@ public function stringify(mixed $raw, int $depth): ?string
 
         return $this->quoter->quote(
             $this->format($raw, 'jsonSerialize() =>', $this->stringifier->stringify($raw->jsonSerialize(), $depth + 1)),
-            $depth
+            $depth,
         );
     }
 }
diff --git a/src/Stringifiers/NotANumberStringifier.php b/src/Stringifiers/NotANumberStringifier.php
index 9487cc2..63d1f52 100644
--- a/src/Stringifiers/NotANumberStringifier.php
+++ b/src/Stringifiers/NotANumberStringifier.php
@@ -19,11 +19,11 @@
 final class NotANumberStringifier implements Stringifier
 {
     public function __construct(
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!is_float($raw)) {
             return null;
diff --git a/src/Stringifiers/NullStringifier.php b/src/Stringifiers/NullStringifier.php
index cd2c3b8..a110e34 100644
--- a/src/Stringifiers/NullStringifier.php
+++ b/src/Stringifiers/NullStringifier.php
@@ -16,11 +16,11 @@
 final class NullStringifier implements Stringifier
 {
     public function __construct(
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if ($raw !== null) {
             return null;
diff --git a/src/Stringifiers/ObjectStringifier.php b/src/Stringifiers/ObjectStringifier.php
index d13a3a1..914e76a 100644
--- a/src/Stringifiers/ObjectStringifier.php
+++ b/src/Stringifiers/ObjectStringifier.php
@@ -25,17 +25,17 @@ final class ObjectStringifier implements Stringifier
 {
     use ObjectHelper;
 
-    private const LIMIT_EXCEEDED_PLACEHOLDER = '...';
+    private const string LIMIT_EXCEEDED_PLACEHOLDER = '...';
 
     public function __construct(
         private readonly Stringifier $stringifier,
         private readonly Quoter $quoter,
         private readonly int $maximumDepth,
-        private readonly int $maximumNumberOfProperties
+        private readonly int $maximumNumberOfProperties,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!is_object($raw)) {
             return null;
@@ -47,13 +47,11 @@ public function stringify(mixed $raw, int $depth): ?string
 
         return $this->quoter->quote(
             $this->format($raw, ...$this->getProperties(new ReflectionObject($raw), $raw, $depth + 1)),
-            $depth
+            $depth,
         );
     }
 
-    /**
-     * @return array<int, string>
-     */
+    /** @return array<int, string> */
     private function getProperties(ReflectionObject $reflectionObject, object $object, int $depth): array
     {
         $reflectionProperties = $reflectionObject->getProperties();
@@ -76,14 +74,14 @@ private function getProperties(ReflectionObject $reflectionObject, object $objec
                     default => '+',
                 },
                 $reflectionProperty->getName(),
-                $this->getPropertyValue($reflectionProperty, $object, $depth)
+                $this->getPropertyValue($reflectionProperty, $object, $depth),
             ));
         }
 
         return $properties;
     }
 
-    private function getPropertyValue(ReflectionProperty $reflectionProperty, object $object, int $depth): ?string
+    private function getPropertyValue(ReflectionProperty $reflectionProperty, object $object, int $depth): string|null
     {
         if (!$reflectionProperty->isInitialized($object)) {
             return '*uninitialized*';
diff --git a/src/Stringifiers/ObjectWithDebugInfoStringifier.php b/src/Stringifiers/ObjectWithDebugInfoStringifier.php
index 2718620..f1cca8a 100644
--- a/src/Stringifiers/ObjectWithDebugInfoStringifier.php
+++ b/src/Stringifiers/ObjectWithDebugInfoStringifier.php
@@ -23,11 +23,11 @@ final class ObjectWithDebugInfoStringifier implements Stringifier
 
     public function __construct(
         private readonly Stringifier $stringifier,
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!(is_object($raw) && method_exists($raw, '__debugInfo'))) {
             return null;
@@ -35,7 +35,7 @@ public function stringify(mixed $raw, int $depth): ?string
 
         return $this->quoter->quote(
             $this->format($raw, '__debugInfo() =>', $this->stringifier->stringify($raw->__debugInfo(), $depth + 1)),
-            $depth
+            $depth,
         );
     }
 }
diff --git a/src/Stringifiers/ResourceStringifier.php b/src/Stringifiers/ResourceStringifier.php
index c8707cf..0f55406 100644
--- a/src/Stringifiers/ResourceStringifier.php
+++ b/src/Stringifiers/ResourceStringifier.php
@@ -20,11 +20,11 @@
 final class ResourceStringifier implements Stringifier
 {
     public function __construct(
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!is_resource($raw)) {
             return null;
diff --git a/src/Stringifiers/StringableObjectStringifier.php b/src/Stringifiers/StringableObjectStringifier.php
index 4aff4d6..121e9dc 100644
--- a/src/Stringifiers/StringableObjectStringifier.php
+++ b/src/Stringifiers/StringableObjectStringifier.php
@@ -21,11 +21,11 @@ final class StringableObjectStringifier implements Stringifier
 
     public function __construct(
         private readonly Stringifier $stringifier,
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!$raw instanceof Stringable) {
             return null;
@@ -33,7 +33,7 @@ public function stringify(mixed $raw, int $depth): ?string
 
         return $this->quoter->quote(
             $this->format($raw, '__toString() =>', $this->stringifier->stringify($raw->__toString(), $depth + 1)),
-            $depth
+            $depth,
         );
     }
 }
diff --git a/src/Stringifiers/ThrowableObjectStringifier.php b/src/Stringifiers/ThrowableObjectStringifier.php
index ab912af..9e4a2f8 100644
--- a/src/Stringifiers/ThrowableObjectStringifier.php
+++ b/src/Stringifiers/ThrowableObjectStringifier.php
@@ -24,11 +24,11 @@ final class ThrowableObjectStringifier implements Stringifier
 
     public function __construct(
         private readonly Stringifier $stringifier,
-        private readonly Quoter $quoter
+        private readonly Quoter $quoter,
     ) {
     }
 
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         if (!$raw instanceof Throwable) {
             return null;
@@ -43,9 +43,9 @@ public function stringify(mixed $raw, int $depth): ?string
                 $raw,
                 $this->stringifier->stringify($raw->getMessage(), $depth + 1),
                 'in',
-                $this->getSource($raw)
+                $this->getSource($raw),
             ),
-            $depth
+            $depth,
         );
     }
 
diff --git a/src/Stringify.php b/src/Stringify.php
index c5f015e..3462365 100644
--- a/src/Stringify.php
+++ b/src/Stringify.php
@@ -16,10 +16,10 @@
 
 final class Stringify
 {
-    public const STARTING_DEPTH = 0;
+    public const int STARTING_DEPTH = 0;
 
     public function __construct(
-        private readonly Stringifier $stringifier
+        private readonly Stringifier $stringifier,
     ) {
     }
 
diff --git a/tests/fixtures/ConcreteIterator.php b/tests/fixtures/ConcreteIterator.php
index a7f1622..604e689 100644
--- a/tests/fixtures/ConcreteIterator.php
+++ b/tests/fixtures/ConcreteIterator.php
@@ -8,12 +8,10 @@
 
 declare(strict_types=1);
 
-/**
- * @implements Iterator<int>
- */
+/** @implements Iterator<int> */
 final class ConcreteIterator implements Iterator
 {
-    private const VALUES = [1, 2, 3];
+    private const array VALUES = [1, 2, 3];
 
     private int $position = 0;
 
diff --git a/tests/fixtures/ConcreteJsonSerializable.php b/tests/fixtures/ConcreteJsonSerializable.php
index 9bb555f..2a4b4f2 100644
--- a/tests/fixtures/ConcreteJsonSerializable.php
+++ b/tests/fixtures/ConcreteJsonSerializable.php
@@ -10,11 +10,9 @@
 
 final class ConcreteJsonSerializable implements JsonSerializable
 {
-    public const JSON_VALUE = [1, 2, 3, 'foo' => true];
+    public const array JSON_VALUE = [1, 2, 3, 'foo' => true];
 
-    /**
-     * @return array<mixed, mixed>
-     */
+    /** @return array<mixed, mixed> */
     public function jsonSerialize(): array
     {
         return self::JSON_VALUE;
diff --git a/tests/fixtures/WithDebugInfo.php b/tests/fixtures/WithDebugInfo.php
index b17534e..a9eb222 100644
--- a/tests/fixtures/WithDebugInfo.php
+++ b/tests/fixtures/WithDebugInfo.php
@@ -10,9 +10,7 @@
 
 final class WithDebugInfo
 {
-    /**
-     * @return array<string, string>
-     */
+    /** @return array<string, string> */
     public function __debugInfo(): array
     {
         return ['info' => 'This is the return of __debugInfo()'];
diff --git a/tests/fixtures/WithMethods.php b/tests/fixtures/WithMethods.php
index 2ecddf4..7dc2afb 100644
--- a/tests/fixtures/WithMethods.php
+++ b/tests/fixtures/WithMethods.php
@@ -10,9 +10,9 @@
 
 final class WithMethods
 {
-    public function publicMethod(Iterator&Countable $parameter): ?static
+    public function publicMethod(Iterator&Countable $parameter): static|null
     {
-        return new static();
+        return $parameter instanceof SplHeap ? new static() : null;
     }
 
     public static function publicStaticMethod(int|float $parameter): void
diff --git a/tests/integration/stringify-array.phpt b/tests/integration/stringify-array.phpt
index 0ec6ba7..ae5bee0 100644
--- a/tests/integration/stringify-array.phpt
+++ b/tests/integration/stringify-array.phpt
@@ -12,11 +12,8 @@ output([
         1.000,
         [
             tmpfile(),
-            [
-                1,
-            ],
-            [
-            ],
+            [1],
+            [],
         ],
     ],
     false,
diff --git a/tests/integration/stringify-callable.phpt b/tests/integration/stringify-callable.phpt
index 8d23380..4ad861d 100644
--- a/tests/integration/stringify-callable.phpt
+++ b/tests/integration/stringify-callable.phpt
@@ -16,7 +16,7 @@ outputMultiple(
     static fn(int $foo): bool => (bool) $foo,
     static function (int $foo) use ($variable): string {
         return $variable::class;
-    }
+    },
 );
 ?>
 --EXPECT--
diff --git a/tests/src/Double/FakeQuoter.php b/tests/src/Double/FakeQuoter.php
index d2cf4b1..d56e395 100644
--- a/tests/src/Double/FakeQuoter.php
+++ b/tests/src/Double/FakeQuoter.php
@@ -16,7 +16,7 @@
 
 final class FakeQuoter implements Quoter
 {
-    private const SYMBOL = '#';
+    private const string SYMBOL = '#';
 
     public function quote(string $string, int $depth): string
     {
diff --git a/tests/src/Double/FakeStringifier.php b/tests/src/Double/FakeStringifier.php
index 15d540c..1c871bb 100644
--- a/tests/src/Double/FakeStringifier.php
+++ b/tests/src/Double/FakeStringifier.php
@@ -18,7 +18,7 @@
 
 final class FakeStringifier implements Stringifier
 {
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string
     {
         return implode('.', ['fake', $depth, hash('crc32', serialize($raw))]);
     }
diff --git a/tests/src/Double/LameStringifier.php b/tests/src/Double/LameStringifier.php
index 6e8d7b4..fb8ca38 100644
--- a/tests/src/Double/LameStringifier.php
+++ b/tests/src/Double/LameStringifier.php
@@ -14,7 +14,7 @@
 
 final class LameStringifier implements Stringifier
 {
-    public function stringify(mixed $raw, int $depth): ?string
+    public function stringify(mixed $raw, int $depth): string|null
     {
         return null;
     }
diff --git a/tests/unit/Quoters/StandardQuoterTest.php b/tests/unit/Quoters/StandardQuoterTest.php
index 50aafb6..ea476e2 100644
--- a/tests/unit/Quoters/StandardQuoterTest.php
+++ b/tests/unit/Quoters/StandardQuoterTest.php
@@ -21,7 +21,7 @@
 #[CoversClass(StandardQuoter::class)]
 final class StandardQuoterTest extends TestCase
 {
-    private const LIMIT = 20;
+    private const int LIMIT = 20;
 
     #[Test]
     public function itShouldNotQuoteWhenDepthIsBiggerThanZero(): void
@@ -46,9 +46,7 @@ public function isShouldQuoteWhenDepthIsBiggerThanZero(string $string, string $e
         self::assertLessThanOrEqual(self::LIMIT, strlen($actual));
     }
 
-    /**
-     * @return array<int, array<int, string>>
-     */
+    /** @return array<int, array<int, string>> */
     public static function provideData(): array
     {
         return [
diff --git a/tests/unit/Stringifiers/ArrayObjectStringifierTest.php b/tests/unit/Stringifiers/ArrayObjectStringifierTest.php
index f2b45df..fc634a1 100644
--- a/tests/unit/Stringifiers/ArrayObjectStringifierTest.php
+++ b/tests/unit/Stringifiers/ArrayObjectStringifierTest.php
@@ -24,7 +24,7 @@
 #[CoversClass(ArrayObjectStringifier::class)]
 final class ArrayObjectStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItIsNotAnArrayObject(): void
@@ -49,7 +49,7 @@ public function itShouldStringifyRawValueWhenItIsAnArrayObject(): void
         $actual = $sut->stringify($raw, self::DEPTH);
         $expected = $quoter->quote(
             sprintf('ArrayObject { getArrayCopy() => %s }', $string),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expected, $actual);
diff --git a/tests/unit/Stringifiers/ArrayStringifierTest.php b/tests/unit/Stringifiers/ArrayStringifierTest.php
index 958b141..ef16b66 100644
--- a/tests/unit/Stringifiers/ArrayStringifierTest.php
+++ b/tests/unit/Stringifiers/ArrayStringifierTest.php
@@ -63,9 +63,9 @@ public function itShouldStringifyRawValueWhenItIsAnNonAssociativeArray(): void
                 '[%s, %s, %s]',
                 $stringifier->stringify($raw[0], $depth + 1),
                 $stringifier->stringify($raw[1], $depth + 1),
-                $stringifier->stringify($raw[2], $depth + 1)
+                $stringifier->stringify($raw[2], $depth + 1),
             ),
-            $depth
+            $depth,
         );
 
         self::assertSame($expected, $actual);
@@ -91,7 +91,7 @@ public function itShouldStringifyRawValueWhenItIsAnAssociativeArray(): void
                 $stringifier->stringify('bar', $depth + 1),
                 $stringifier->stringify($raw['bar'], $depth + 1),
             ),
-            $depth
+            $depth,
         );
 
         self::assertSame($expected, $actual);
@@ -115,7 +115,7 @@ public function itShouldStringifyRawValueWhenIsNotSequentialArray(): void
                 $stringifier->stringify(2, $depth + 1),
                 $stringifier->stringify(3, $depth + 1),
             ),
-            $depth
+            $depth,
         );
 
         self::assertSame($expected, $sut->stringify($raw, $depth));
@@ -148,13 +148,13 @@ public function itShouldStringifyRawValueWhenItIsNestedArray(): void
                                 $stringifier->stringify('d', $depth + 3),
                                 $stringifier->stringify('e', $depth + 3),
                             ),
-                            $depth + 2
-                        )
+                            $depth + 2,
+                        ),
                     ),
-                    $depth + 1
+                    $depth + 1,
                 ),
             ),
-            $depth
+            $depth,
         );
 
         self::assertSame($expected, $actual);
@@ -224,13 +224,13 @@ public function itShouldStringifyRawValueWithPlaceholderWhenItReachesTheMaximumD
                                 $stringifier->stringify('c', $depth + 3),
                                 $quoter->quote('...', $depth + 3),
                             ),
-                            $depth + 2
-                        )
+                            $depth + 2,
+                        ),
                     ),
-                    $depth + 1
+                    $depth + 1,
                 ),
             ),
-            $depth
+            $depth,
         );
 
         self::assertSame($expected, $actual);
@@ -256,7 +256,7 @@ public function itShouldStringifyRawValueWithPlaceholderWhenLimitOfItemsIsReache
                 $stringifier->stringify(2, $depth + 1),
                 $stringifier->stringify(3, $depth + 1),
             ),
-            $depth
+            $depth,
         );
         $actual = $sut->stringify($raw, $depth);
 
diff --git a/tests/unit/Stringifiers/BoolStringifierTest.php b/tests/unit/Stringifiers/BoolStringifierTest.php
index 872f4e8..51a2a68 100644
--- a/tests/unit/Stringifiers/BoolStringifierTest.php
+++ b/tests/unit/Stringifiers/BoolStringifierTest.php
@@ -19,7 +19,7 @@
 #[CoversClass(BoolStringifier::class)]
 final class BoolStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyWhenRawValueIsNotBoolean(): void
diff --git a/tests/unit/Stringifiers/CallableStringifierTest.php b/tests/unit/Stringifiers/CallableStringifierTest.php
index 23e063f..fb298bb 100644
--- a/tests/unit/Stringifiers/CallableStringifierTest.php
+++ b/tests/unit/Stringifiers/CallableStringifierTest.php
@@ -17,7 +17,6 @@
 use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
-use Respect\Stringifier\Helpers\ObjectHelper;
 use Respect\Stringifier\Stringifiers\CallableStringifier;
 use Respect\Stringifier\Test\Double\FakeQuoter;
 use Respect\Stringifier\Test\Double\FakeStringifier;
@@ -25,14 +24,10 @@
 use function array_sum;
 use function sprintf;
 
-use const PHP_MAJOR_VERSION;
-use const PHP_MINOR_VERSION;
-
-#[CoversClass(ObjectHelper::class)]
 #[CoversClass(CallableStringifier::class)]
 final class CallableStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyWhenRawValueIsNotCallable(): void
@@ -69,7 +64,7 @@ public function itShouldStringifyWhenRawValueIsCallableWithDefaultValues(): void
         $actual = $sut->stringify($raw, self::DEPTH);
         $expected = $quoter->quote(
             sprintf('function (int $value = %s): int', $stringifier->stringify(1, self::DEPTH + 1)),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertEquals($expected, $actual);
@@ -78,10 +73,6 @@ public function itShouldStringifyWhenRawValueIsCallableWithDefaultValues(): void
     #[Test]
     public function itShouldStringifyWhenRawValueIsCallableThatDoesNotHaveAnAccessibleDefaultValue(): void
     {
-        if ([8, 1] !== [PHP_MAJOR_VERSION, PHP_MINOR_VERSION]) {
-            self::markTestSkipped('This test is not applicable to PHP 8.1+');
-        }
-
         $raw = 'array_walk';
 
         $quoter = new FakeQuoter();
@@ -90,16 +81,14 @@ public function itShouldStringifyWhenRawValueIsCallableThatDoesNotHaveAnAccessib
 
         $actual = $sut->stringify($raw, self::DEPTH);
         $expected = $quoter->quote(
-            'array_walk(object|array &$array, callable $callback, ?mixed $arg = fake.1.cbade92e): bool',
-            self::DEPTH
+            'array_walk(object|array &$array, callable $callback, ?mixed $arg = fake.1.cbade92e): true',
+            self::DEPTH,
         );
 
         self::assertEquals($expected, $actual);
     }
 
-    /**
-     * @return array<int, array{0: callable, 1: string}>
-     */
+    /** @return array<int, array{0: callable, 1: string}> */
     public static function callableRawValuesProvider(): array
     {
         $var1 = 1;
@@ -110,6 +99,7 @@ public static function callableRawValuesProvider(): array
             [static fn(): int => 1, 'function (): int'],
             [static fn(float $value): int => (int) $value, 'function (float $value): int'],
             [static fn(float &$value): int => (int) $value, 'function (float &$value): int'],
+            // phpcs:ignore SlevomatCodingStandard.TypeHints.DNFTypeHintFormat
             [static fn(?float $value): int => (int) $value, 'function (?float $value): int'],
             [static fn(int $value = self::DEPTH): int => $value, 'function (int $value = self::DEPTH): int'],
             [static fn(int|float $value): int => (int) $value, 'function (int|float $value): int'],
diff --git a/tests/unit/Stringifiers/CompositeStringifierTest.php b/tests/unit/Stringifiers/CompositeStringifierTest.php
index fbe5099..22b1806 100644
--- a/tests/unit/Stringifiers/CompositeStringifierTest.php
+++ b/tests/unit/Stringifiers/CompositeStringifierTest.php
@@ -21,7 +21,7 @@
 #[CoversClass(CompositeStringifier::class)]
 final class CompositeStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenThereAreNoStringifiersDefined(): void
diff --git a/tests/unit/Stringifiers/DateTimeStringifierTest.php b/tests/unit/Stringifiers/DateTimeStringifierTest.php
index 2ad39d0..168ca3e 100644
--- a/tests/unit/Stringifiers/DateTimeStringifierTest.php
+++ b/tests/unit/Stringifiers/DateTimeStringifierTest.php
@@ -17,15 +17,13 @@
 use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
-use Respect\Stringifier\Helpers\ObjectHelper;
 use Respect\Stringifier\Stringifiers\DateTimeStringifier;
 use Respect\Stringifier\Test\Double\FakeQuoter;
 
-#[CoversClass(ObjectHelper::class)]
 #[CoversClass(DateTimeStringifier::class)]
 final class DateTimeStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItIsNotInstanceOfDateTimeInterface(): void
@@ -40,7 +38,7 @@ public function itShouldNotStringifyRawValueWhenItIsNotInstanceOfDateTimeInterfa
     public function itShouldStringifyRawValueWhenItIsInstanceOfDateTimeInterface(
         DateTimeInterface $raw,
         string $format,
-        string $string
+        string $string,
     ): void {
         $quoter = new FakeQuoter();
 
@@ -52,9 +50,7 @@ public function itShouldStringifyRawValueWhenItIsInstanceOfDateTimeInterface(
         self::assertSame($expected, $actual);
     }
 
-    /**
-     * @return array<int, array{0: DateTimeInterface, 1: string, 2: string}>
-     */
+    /** @return array<int, array{0: DateTimeInterface, 1: string, 2: string}> */
     public static function stringableRawValuesProvider(): array
     {
         $dateTime = new DateTime('2017-12-31T23:59:59+00:00');
diff --git a/tests/unit/Stringifiers/DeclaredStringifierTest.php b/tests/unit/Stringifiers/DeclaredStringifierTest.php
index 42efcf2..af2d454 100644
--- a/tests/unit/Stringifiers/DeclaredStringifierTest.php
+++ b/tests/unit/Stringifiers/DeclaredStringifierTest.php
@@ -24,7 +24,7 @@
 #[CoversClass(DeclaredStringifier::class)]
 final class DeclaredStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyWhenRawValueIsNotExists(): void
@@ -48,9 +48,7 @@ public function itShouldStringifyWhenRawValueIsExists(string $raw): void
         self::assertEquals($expected, $actual);
     }
 
-    /**
-     * @return array<int, array<int, string>>
-     */
+    /** @return array<int, array<int, string>> */
     public static function existsRawValuesProvider(): array
     {
         return [
diff --git a/tests/unit/Stringifiers/EnumerationStringifierTest.php b/tests/unit/Stringifiers/EnumerationStringifierTest.php
index 6178b95..a39c9a0 100644
--- a/tests/unit/Stringifiers/EnumerationStringifierTest.php
+++ b/tests/unit/Stringifiers/EnumerationStringifierTest.php
@@ -21,7 +21,7 @@
 #[CoversClass(EnumerationStringifier::class)]
 final class EnumerationStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyWhenRawValueIsNotAnEnumeration(): void
diff --git a/tests/unit/Stringifiers/FiberObjectStringifierTest.php b/tests/unit/Stringifiers/FiberObjectStringifierTest.php
index fe1ced3..20b8c9d 100644
--- a/tests/unit/Stringifiers/FiberObjectStringifierTest.php
+++ b/tests/unit/Stringifiers/FiberObjectStringifierTest.php
@@ -25,7 +25,7 @@
 #[CoversClass(FiberObjectStringifier::class)]
 final class FiberObjectStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItIsNotAnObjectWithDebugInfo(): void
@@ -52,7 +52,7 @@ public function itShouldStringifyRawValueWhenItIsAnObjectWithDebugInfo(): void
         $actual = $sut->stringify($raw, self::DEPTH);
         $expected = $quoter->quote(
             sprintf('Fiber { %s }', $string),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expected, $actual);
diff --git a/tests/unit/Stringifiers/InfiniteNumberStringifierTest.php b/tests/unit/Stringifiers/InfiniteNumberStringifierTest.php
index 060feba..aadfe46 100644
--- a/tests/unit/Stringifiers/InfiniteNumberStringifierTest.php
+++ b/tests/unit/Stringifiers/InfiniteNumberStringifierTest.php
@@ -21,7 +21,7 @@
 #[CoversClass(InfiniteNumberStringifier::class)]
 final class InfiniteNumberStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItIsNotFloat(): void
diff --git a/tests/unit/Stringifiers/IteratorObjectStringifierTest.php b/tests/unit/Stringifiers/IteratorObjectStringifierTest.php
index e54fa1f..1059855 100644
--- a/tests/unit/Stringifiers/IteratorObjectStringifierTest.php
+++ b/tests/unit/Stringifiers/IteratorObjectStringifierTest.php
@@ -15,18 +15,16 @@
 use PHPUnit\Framework\Attributes\CoversClass;
 use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
-use Respect\Stringifier\Helpers\ObjectHelper;
 use Respect\Stringifier\Stringifiers\IteratorObjectStringifier;
 use Respect\Stringifier\Test\Double\FakeQuoter;
 use Respect\Stringifier\Test\Double\FakeStringifier;
 
 use function sprintf;
 
-#[CoversClass(ObjectHelper::class)]
 #[CoversClass(IteratorObjectStringifier::class)]
 final class IteratorObjectStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItIsNotTraversable(): void
@@ -60,7 +58,7 @@ public function itShouldStringifyRawValueWhenItIsAnInstanceOfIterator(): void
                 'ConcreteIterator { current() => %s }',
                 $stringifier->stringify($raw->current(), self::DEPTH + 1),
             ),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expected, $actual);
diff --git a/tests/unit/Stringifiers/JsonEncodableStringifierTest.php b/tests/unit/Stringifiers/JsonEncodableStringifierTest.php
index 095322d..f8c84e4 100644
--- a/tests/unit/Stringifiers/JsonEncodableStringifierTest.php
+++ b/tests/unit/Stringifiers/JsonEncodableStringifierTest.php
@@ -20,7 +20,7 @@
 #[CoversClass(JsonEncodableStringifier::class)]
 final class JsonEncodableStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItCannotBeConvertedToJson(): void
diff --git a/tests/unit/Stringifiers/JsonSerializableObjectStringifierTest.php b/tests/unit/Stringifiers/JsonSerializableObjectStringifierTest.php
index 4b8751a..5fcf4c7 100644
--- a/tests/unit/Stringifiers/JsonSerializableObjectStringifierTest.php
+++ b/tests/unit/Stringifiers/JsonSerializableObjectStringifierTest.php
@@ -14,7 +14,6 @@
 use PHPUnit\Framework\Attributes\CoversClass;
 use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
-use Respect\Stringifier\Helpers\ObjectHelper;
 use Respect\Stringifier\Stringifiers\JsonSerializableObjectStringifier;
 use Respect\Stringifier\Test\Double\FakeQuoter;
 use Respect\Stringifier\Test\Double\FakeStringifier;
@@ -22,11 +21,10 @@
 
 use function sprintf;
 
-#[CoversClass(ObjectHelper::class)]
 #[CoversClass(JsonSerializableObjectStringifier::class)]
 final class JsonSerializableObjectStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItIsNotAnInstanceOfJsonSerializable(): void
@@ -50,7 +48,7 @@ public function itShouldStringifyRawValueWhenItIsAnInstanceOfJsonSerializable():
         $actual = $sut->stringify($raw, self::DEPTH);
         $expected = $quoter->quote(
             sprintf('%s { jsonSerialize() => %s }', ConcreteJsonSerializable::class, $jsonString),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expected, $actual);
diff --git a/tests/unit/Stringifiers/NotANumberStringifierTest.php b/tests/unit/Stringifiers/NotANumberStringifierTest.php
index f53b321..f89aa7f 100644
--- a/tests/unit/Stringifiers/NotANumberStringifierTest.php
+++ b/tests/unit/Stringifiers/NotANumberStringifierTest.php
@@ -21,7 +21,7 @@
 #[CoversClass(NotANumberStringifier::class)]
 final class NotANumberStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItIsNotFloat(): void
diff --git a/tests/unit/Stringifiers/NullStringifierTest.php b/tests/unit/Stringifiers/NullStringifierTest.php
index 0c00837..b09a89e 100644
--- a/tests/unit/Stringifiers/NullStringifierTest.php
+++ b/tests/unit/Stringifiers/NullStringifierTest.php
@@ -19,7 +19,7 @@
 #[CoversClass(NullStringifier::class)]
 final class NullStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItIsNotNull(): void
diff --git a/tests/unit/Stringifiers/ObjectStringifierTest.php b/tests/unit/Stringifiers/ObjectStringifierTest.php
index f157173..7dd3565 100644
--- a/tests/unit/Stringifiers/ObjectStringifierTest.php
+++ b/tests/unit/Stringifiers/ObjectStringifierTest.php
@@ -27,9 +27,9 @@
 #[CoversClass(ObjectStringifier::class)]
 final class ObjectStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
-    private const MAXIMUM_DEPTH = 4;
-    private const MAXIMUM_NUMBER_OF_PROPERTIES = 5;
+    private const int DEPTH = 0;
+    private const int MAXIMUM_DEPTH = 4;
+    private const int MAXIMUM_NUMBER_OF_PROPERTIES = 5;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItIsNotAnObject(): void
@@ -38,7 +38,7 @@ public function itShouldNotStringifyRawValueWhenItIsNotAnObject(): void
             new FakeStringifier(),
             new FakeQuoter(),
             self::MAXIMUM_DEPTH,
-            self::MAXIMUM_NUMBER_OF_PROPERTIES
+            self::MAXIMUM_NUMBER_OF_PROPERTIES,
         );
 
         self::assertNull($sut->stringify(true, self::DEPTH));
@@ -81,7 +81,7 @@ public function itShouldStringifyRawValueWhenItIsAnObjectWithProperties(): void
                 $stringifier->stringify($relection->getProperty('protectedProperty')->getValue($raw), self::DEPTH + 1),
                 $stringifier->stringify($relection->getProperty('privateProperty')->getValue($raw), self::DEPTH + 1),
             ),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expected, $actual);
@@ -106,7 +106,7 @@ public function itShouldStringifyRawValueWhenItIsAnObjectWithUninitializedProper
                 $relection->getName(),
                 '*uninitialized*',
             ),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expected, $actual);
@@ -141,15 +141,15 @@ public function itShouldStringifyRawValueWhenItIsAnObjectWithPropertiesThatAreOb
                             sprintf(
                                 'stdClass { +$e=%s +$f=%s }',
                                 $stringifier->stringify($raw->b->d->e, self::DEPTH + 3),
-                                $quoter->quote('stdClass {}', self::DEPTH + 3)
+                                $quoter->quote('stdClass {}', self::DEPTH + 3),
                             ),
-                            self::DEPTH + 2
-                        )
+                            self::DEPTH + 2,
+                        ),
                     ),
-                    self::DEPTH + 1
-                )
+                    self::DEPTH + 1,
+                ),
             ),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expected, $actual);
@@ -178,15 +178,15 @@ public function itShouldStringifyRawValueWithPlaceholderWhenItReachesTheMaximumD
                         $quoter->quote(
                             sprintf(
                                 'stdClass { +$property=%s }',
-                                $quoter->quote('stdClass { ... }', $maximumDepth)
+                                $quoter->quote('stdClass { ... }', $maximumDepth),
                             ),
-                            self::DEPTH + 2
-                        )
+                            self::DEPTH + 2,
+                        ),
                     ),
-                    self::DEPTH + 1
-                )
+                    self::DEPTH + 1,
+                ),
             ),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expected, $actual);
@@ -216,7 +216,7 @@ public function itShouldStringifyRawValueWithPlaceholderWhenItReachesLimitOfItem
                 $stringifier->stringify($raw->b, self::DEPTH + 1),
                 $stringifier->stringify($raw->c, self::DEPTH + 1),
             ),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expected, $actual);
@@ -238,9 +238,9 @@ public function itShouldStringifyRawValueWhenItIsAnAnonymousClass(): void
         $expected = $quoter->quote(
             sprintf(
                 'class { +$foo=%s }',
-                $stringifier->stringify($raw->foo, self::DEPTH + 1)
+                $stringifier->stringify($raw->foo, self::DEPTH + 1),
             ),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expected, $actual);
@@ -258,7 +258,7 @@ public function itShouldStringifyRawValueWhenItIsAnAnonymousClassExtendingAnothe
             new FakeStringifier(),
             $quoter,
             self::MAXIMUM_DEPTH,
-            self::MAXIMUM_NUMBER_OF_PROPERTIES
+            self::MAXIMUM_NUMBER_OF_PROPERTIES,
         );
 
         $actual = $sut->stringify($raw, self::DEPTH);
diff --git a/tests/unit/Stringifiers/ObjectWithDebugInfoStringifierTest.php b/tests/unit/Stringifiers/ObjectWithDebugInfoStringifierTest.php
index 3189c2f..aa6e3b7 100644
--- a/tests/unit/Stringifiers/ObjectWithDebugInfoStringifierTest.php
+++ b/tests/unit/Stringifiers/ObjectWithDebugInfoStringifierTest.php
@@ -13,7 +13,6 @@
 use PHPUnit\Framework\Attributes\CoversClass;
 use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
-use Respect\Stringifier\Helpers\ObjectHelper;
 use Respect\Stringifier\Stringifiers\ObjectWithDebugInfoStringifier;
 use Respect\Stringifier\Test\Double\FakeQuoter;
 use Respect\Stringifier\Test\Double\FakeStringifier;
@@ -22,11 +21,10 @@
 
 use function sprintf;
 
-#[CoversClass(ObjectHelper::class)]
 #[CoversClass(ObjectWithDebugInfoStringifier::class)]
 final class ObjectWithDebugInfoStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItIsNotAnObjectWithDebugInfo(): void
@@ -51,7 +49,7 @@ public function itShouldStringifyRawValueWhenItIsAnObjectWithDebugInfo(): void
         $actual = $sut->stringify($raw, self::DEPTH);
         $expected = $quoter->quote(
             sprintf('%s { __debugInfo() => %s }', WithDebugInfo::class, $string),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expected, $actual);
diff --git a/tests/unit/Stringifiers/ResourceStringifierTest.php b/tests/unit/Stringifiers/ResourceStringifierTest.php
index 0a4901f..91a26f9 100644
--- a/tests/unit/Stringifiers/ResourceStringifierTest.php
+++ b/tests/unit/Stringifiers/ResourceStringifierTest.php
@@ -21,7 +21,7 @@
 #[CoversClass(ResourceStringifier::class)]
 final class ResourceStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItIsNotOfTypeResource(): void
diff --git a/tests/unit/Stringifiers/StringableObjectStringifierTest.php b/tests/unit/Stringifiers/StringableObjectStringifierTest.php
index d300509..ff2228c 100644
--- a/tests/unit/Stringifiers/StringableObjectStringifierTest.php
+++ b/tests/unit/Stringifiers/StringableObjectStringifierTest.php
@@ -14,7 +14,6 @@
 use PHPUnit\Framework\Attributes\CoversClass;
 use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
-use Respect\Stringifier\Helpers\ObjectHelper;
 use Respect\Stringifier\Stringifiers\StringableObjectStringifier;
 use Respect\Stringifier\Test\Double\FakeQuoter;
 use Respect\Stringifier\Test\Double\FakeStringifier;
@@ -22,11 +21,10 @@
 
 use function sprintf;
 
-#[CoversClass(ObjectHelper::class)]
 #[CoversClass(StringableObjectStringifier::class)]
 final class StringableObjectStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function itShouldNotStringifyRawValueWhenItIsNotAnInstanceOfStringable(): void
@@ -51,7 +49,7 @@ public function itShouldStringifyRawValueWhenItIsAnInstanceOfStringable(): void
         $actual = $sut->stringify($raw, self::DEPTH);
         $expected = $quoter->quote(
             sprintf('%s { __toString() => %s }', ConcreteStringable::class, $string),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expected, $actual);
diff --git a/tests/unit/Stringifiers/ThrowableObjectStringifierTest.php b/tests/unit/Stringifiers/ThrowableObjectStringifierTest.php
index 32ac9b9..4758cdb 100644
--- a/tests/unit/Stringifiers/ThrowableObjectStringifierTest.php
+++ b/tests/unit/Stringifiers/ThrowableObjectStringifierTest.php
@@ -19,7 +19,6 @@
 use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
-use Respect\Stringifier\Helpers\ObjectHelper;
 use Respect\Stringifier\Stringifiers\ThrowableObjectStringifier;
 use Respect\Stringifier\Test\Double\FakeQuoter;
 use Respect\Stringifier\Test\Double\FakeStringifier;
@@ -30,11 +29,10 @@
 
 use function sprintf;
 
-#[CoversClass(ObjectHelper::class)]
 #[CoversClass(ThrowableObjectStringifier::class)]
 final class ThrowableObjectStringifierTest extends TestCase
 {
-    private const DEPTH = 0;
+    private const int DEPTH = 0;
 
     #[Test]
     public function isShouldNotStringifyRawValueWhenItIsNotThrowable(): void
@@ -61,7 +59,7 @@ public function itShouldStringifyRawValueWhenItIsThrowableWithMessage(Throwable
                 $stringifier->stringify($raw->getMessage(), self::DEPTH + 1),
                 $raw->getLine(),
             ),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expectedValue, $actual);
@@ -83,15 +81,13 @@ public function itShouldStringifyRawValueWhenItIsThrowableWithoutMessage(Throwab
                 $raw::class,
                 $raw->getLine(),
             ),
-            self::DEPTH
+            self::DEPTH,
         );
 
         self::assertSame($expectedValue, $actual);
     }
 
-    /**
-     * @return array<array{0: Throwable}>
-     */
+    /** @return array<array{0: Throwable}> */
     public static function throwableWithMessageProvider(): array
     {
         return [
@@ -102,9 +98,7 @@ public static function throwableWithMessageProvider(): array
         ];
     }
 
-    /**
-     * @return array<array{0: Throwable}>
-     */
+    /** @return array<array{0: Throwable}> */
     public static function throwableWithoutMessageProvider(): array
     {
         return [