diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f6b24d8..1dd35a5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,9 +18,6 @@ jobs:
 
       matrix:
         php:
-          - '7.1'
-          - '7.2'
-          - '7.3'
           - '7.4'
           - '8.0'
           - '8.1'
@@ -35,17 +32,13 @@ jobs:
         dependency:
           - 'highest'
         include:
-          - { php: '7.1', symfony: '3.*', dependency: 'lowest' }
+          - { php: '7.4', symfony: '3.*', dependency: 'lowest' }
         exclude:
           - { php: '8.0', symfony: '3.*' }
           - { php: '8.1', symfony: '3.*' }
           - { php: '8.2', symfony: '3.*' }
           - { php: '8.3', symfony: '3.*' }
           - { php: '8.4', symfony: '3.*' }
-          - { php: '7.1', symfony: '5.*' }
-          - { php: '7.1', symfony: '6.*' }
-          - { php: '7.2', symfony: '6.*' }
-          - { php: '7.3', symfony: '6.*' }
           - { php: '7.4', symfony: '6.*' }
           - { php: '8.0', symfony: '6.*' }
 
@@ -60,12 +53,7 @@ jobs:
           tools: flex
 
       - name: Ignore specific Composer audit advisory
-        run: |
-            if [[ "${{ matrix.php }}" == "7.1" ]]; then
-                echo "COMPOSER_AUDIT_BLOCK_INSECURE=0" >> $GITHUB_ENV
-            else
-                composer config --global audit.ignore "PKSA-w2tw-kmfg-rt9s"
-            fi
+        run: composer config --global audit.ignore "PKSA-w2tw-kmfg-rt9s"
 
       - name: Install dependencies
         uses: ramsey/composer-install@v2
diff --git a/CHANGELOG.md b/CHANGELOG.md
index e3f3720..ad5f877 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,45 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## 3.5.0
+### Changed
+- `DateNormalizer::mapToEntity()` rejects `null` up front instead of passing it to
+  `DateTime::createFromFormat()`, resolving a PHP 8.1 deprecation. `null` still raises
+  `InvalidDataException`, so `catch` blocks are unaffected, but the message changes from
+  `Provided date format is invalid` to `Date must be provided` — the old text blamed the
+  configured format for what is really a missing input. Consumers that match on
+  `getMessage()` rather than the exception type, such as API error-mapping layers, need to
+  account for the new string.
+- Narrowed the `phpunit/phpunit` development requirement to `^9.3` — the version that introduced
+  the `<coverage>` configuration element used by `phpunit.xml.dist`.
+- Replaced leading-backslash class references with `use` statements throughout the library —
+  global classes (`ArrayIterator`, `ArrayObject`, `DateTime`, `DateTimeZone`, `Exception` and
+  the SPL exceptions) and fully qualified `Paysera\...` references in docblocks. No behaviour
+  change.
+- Replaced long array syntax (`array(...)`) with short syntax (`[...]`) throughout the library.
+  No behaviour change.
+
+### Removed
+- Dropped support for PHP 7.1, 7.2 and 7.3. Minimum supported version is now PHP 7.4. Projects
+  still on those versions resolve to 3.4.x and are unaffected.
+
+### Fixed
+- `Result::getIterator()` is marked `#[\ReturnTypeWillChange]`, silencing the PHP 8.1 tentative
+  return type deprecation without changing the signature. The native `\Traversable` return type
+  is deferred to 4.0.0, where it will be batched with the other type additions.
+- `CamelCaseToSnakeCaseConverter::convert()` no longer passes `null` to `preg_replace()`,
+  resolving a PHP 8.1 deprecation. Passing `null` still returns an empty string as before.
+- `FollowUpFilter` no longer redeclares `$offset` without an initialiser. The shadowing
+  declaration gave it a `null` default where `Filter` declares `0`; it now inherits the parent
+  default. Instances built through the constructor were always assigned an offset there and are
+  unaffected.
+- `Result::$items` now defaults to an empty array, so iterating a `Result` whose items were never
+  set no longer raises a `TypeError` on PHP 8 (an `InvalidArgumentException` on PHP 7.4) and
+  `getItems()` honours its documented `@return mixed[]`. The default lives on the property
+  declaration rather than in the constructor, so it also applies to instances built without one —
+  `ReflectionClass::newInstanceWithoutConstructor()`, and the ORM hydration and mocking that build
+  on it.
+
 ## 3.4.0
 ### Added
 - PHP 8.4 support, removed implicitly nullable parameter declarations.
diff --git a/composer.json b/composer.json
index e54890a..624ac9b 100644
--- a/composer.json
+++ b/composer.json
@@ -12,10 +12,10 @@
         }
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.0 || ^8.0 || ^9.0"
+        "phpunit/phpunit": "^9.3"
     },
     "require": {
-        "php": "^7.1 || ^8.0",
+        "php": "^7.4 || ^8.0",
         "symfony/property-access": "^3.0 || ^4.0 || ^5.0 || ^6.0",
         "symfony/validator": "^3.0 || ^4.0 || ^5.0 || ^6.0",
         "willdurand/jsonp-callback-validator": "^1.0"
diff --git a/src/Converter/CamelCaseToSnakeCaseConverter.php b/src/Converter/CamelCaseToSnakeCaseConverter.php
index 0cf1422..78338df 100644
--- a/src/Converter/CamelCaseToSnakeCaseConverter.php
+++ b/src/Converter/CamelCaseToSnakeCaseConverter.php
@@ -13,7 +13,7 @@ public function convert($path)
                 preg_replace(
                     '/[A-Z]/u',
                     '_$0',
-                    $path
+                    $path ?? ''
                 )
             ),
             '_'
diff --git a/src/Encoding/Jsonp.php b/src/Encoding/Jsonp.php
index 4b125e0..b356ebe 100644
--- a/src/Encoding/Jsonp.php
+++ b/src/Encoding/Jsonp.php
@@ -7,7 +7,6 @@
 
 class Jsonp implements EncoderInterface
 {
-
     protected $jsonEncoder;
 
     protected $callbackValidator;
@@ -57,10 +56,10 @@ public function encode($data)
                 $this->jsonEncoder->decode($this->parameter);
             } catch (EncodingException $exception) {
                 $this->parameter = null;
-                $json = $this->jsonEncoder->encode(array(
+                $json = $this->jsonEncoder->encode([
                     'error' => 'invalid_parameters',
                     'error_description' => 'Passed parameter must be valid JSON string',
-                ));
+                ]);
             }
         }
 
diff --git a/src/Entity/FollowUpFilter.php b/src/Entity/FollowUpFilter.php
index c7a7647..18ad7f7 100644
--- a/src/Entity/FollowUpFilter.php
+++ b/src/Entity/FollowUpFilter.php
@@ -4,11 +4,6 @@
 
 class FollowUpFilter extends Filter
 {
-    /**
-     * @var int
-     */
-    protected $offset;
-
     /**
      * @var int
      */
diff --git a/src/Entity/Result.php b/src/Entity/Result.php
index ea7f3e7..d077fc8 100644
--- a/src/Entity/Result.php
+++ b/src/Entity/Result.php
@@ -2,7 +2,13 @@
 
 namespace Paysera\Component\Serializer\Entity;
 
-class Result implements \IteratorAggregate, ResultInterface
+use ArrayIterator;
+use BadMethodCallException;
+use IteratorAggregate;
+use ReturnTypeWillChange;
+use Traversable;
+
+class Result implements IteratorAggregate, ResultInterface
 {
     /**
      * @var int
@@ -37,8 +43,7 @@ class Result implements \IteratorAggregate, ResultInterface
     /**
      * @var mixed[]
      */
-    protected $items;
-
+    protected $items = [];
 
     public function __construct(?Filter $filter = null)
     {
@@ -201,14 +206,14 @@ public function addItem($item)
     /**
      * Try to calculate total result count, in case all results are fetched.
      *
-     * @param $resultCount
-     * @return null
-     * @throws \BadMethodCallException
+     * @param int $resultCount
+     * @return int|null the calculated total count, or null when it cannot be determined
+     * @throws BadMethodCallException
      */
     public function calculateTotalCount($resultCount)
     {
         if (!$this->getFilter()) {
-            throw new \BadMethodCallException('filter must be set before calling this method');
+            throw new BadMethodCallException('filter must be set before calling this method');
         }
 
         if (
@@ -226,10 +231,11 @@ public function calculateTotalCount($resultCount)
     /**
      * Retrieve an external iterator
      *
-     * @return \Traversable
+     * @return Traversable
      */
+    #[ReturnTypeWillChange]
     public function getIterator()
     {
-        return new \ArrayIterator($this->items);
+        return new ArrayIterator($this->items);
     }
 }
diff --git a/src/Entity/ResultInterface.php b/src/Entity/ResultInterface.php
index 3afbc99..1293c38 100644
--- a/src/Entity/ResultInterface.php
+++ b/src/Entity/ResultInterface.php
@@ -2,7 +2,9 @@
 
 namespace Paysera\Component\Serializer\Entity;
 
-interface ResultInterface extends \Traversable
+use Traversable;
+
+interface ResultInterface extends Traversable
 {
     /**
      * Gets totalCount
diff --git a/src/Exception/EncodingException.php b/src/Exception/EncodingException.php
index e0f0d92..e8a5cf1 100644
--- a/src/Exception/EncodingException.php
+++ b/src/Exception/EncodingException.php
@@ -2,6 +2,8 @@
 
 namespace Paysera\Component\Serializer\Exception;
 
-class EncodingException extends \Exception
+use Exception;
+
+class EncodingException extends Exception
 {
 }
diff --git a/src/Factory/ContextAwareNormalizerFactory.php b/src/Factory/ContextAwareNormalizerFactory.php
index 67bb4f1..9459e5d 100644
--- a/src/Factory/ContextAwareNormalizerFactory.php
+++ b/src/Factory/ContextAwareNormalizerFactory.php
@@ -4,21 +4,20 @@
 
 use Paysera\Component\Serializer\Filter\FieldsFilter;
 use Paysera\Component\Serializer\Filter\FieldsParser;
+use Paysera\Component\Serializer\Normalizer\ContextAwareNormalizerInterface;
 use Paysera\Component\Serializer\Normalizer\DenormalizerInterface;
 use Paysera\Component\Serializer\Normalizer\DistributedNormalizer;
-use Paysera\Component\Serializer\Normalizer\ContextAwareNormalizerInterface;
 use Paysera\Component\Serializer\Normalizer\NormalizerInterface;
 
 class ContextAwareNormalizerFactory
 {
-
     /**
-     * @var \Paysera\Component\Serializer\Filter\FieldsFilter
+     * @var FieldsFilter
      */
     protected $fieldsFilter;
 
     /**
-     * @var \Paysera\Component\Serializer\Filter\FieldsParser
+     * @var FieldsParser
      */
     protected $fieldsParser;
 
@@ -44,4 +43,4 @@ public function create($normalizer)
             $normalizer
         );
     }
-} 
+}
diff --git a/src/Factory/ResponseMapperFactory.php b/src/Factory/ResponseMapperFactory.php
index d9e863f..83933c0 100644
--- a/src/Factory/ResponseMapperFactory.php
+++ b/src/Factory/ResponseMapperFactory.php
@@ -3,6 +3,7 @@
 namespace Paysera\Component\Serializer\Factory;
 
 use Paysera\Component\Serializer\Normalizer\NormalizerInterface;
+use RuntimeException;
 
 class ResponseMapperFactory implements ResponseMapperFactoryInterface
 {
@@ -22,7 +23,7 @@ class ResponseMapperFactory implements ResponseMapperFactoryInterface
     public function __construct(NormalizerInterface $defaultMapper)
     {
         $this->defaultMapper = $defaultMapper;
-        $this->mappers = array();
+        $this->mappers = [];
     }
 
     /**
@@ -40,14 +41,14 @@ public function addMapper($key, NormalizerInterface $mapper)
     /**
      * @param array $options
      *
-     * @throws \RuntimeException
+     * @throws RuntimeException
      * @return NormalizerInterface
      */
     public function createResponseMapper(array $options)
     {
         $key = isset($options[self::MAPPER_OPTION]) ? $options[self::MAPPER_OPTION] : null;
         if ($key !== null && !isset($this->mappers[$key])) {
-            throw new \RuntimeException('Wrong mapper key specified: ' . $key);
+            throw new RuntimeException('Wrong mapper key specified: ' . $key);
         }
         if ($key === null) {
             foreach ($options as $optionKey => $value) {
@@ -58,4 +59,4 @@ public function createResponseMapper(array $options)
         }
         return $key !== null ? $this->mappers[$key] : $this->defaultMapper;
     }
-} 
+}
diff --git a/src/Filter/FieldsConfig.php b/src/Filter/FieldsConfig.php
index 7b9dff9..d256c3e 100644
--- a/src/Filter/FieldsConfig.php
+++ b/src/Filter/FieldsConfig.php
@@ -55,7 +55,7 @@ public function getFieldExtensions($fieldName)
             }
             return $extensions;
         } else {
-            return $this->defaultsIncluded ? array('*') : array();
+            return $this->defaultsIncluded ? ['*'] : [];
         }
     }
 
@@ -66,4 +66,4 @@ public function areDefaultsIncluded()
     {
         return $this->defaultsIncluded;
     }
-} 
+}
diff --git a/src/Filter/FieldsFilter.php b/src/Filter/FieldsFilter.php
index 0423384..59de91a 100644
--- a/src/Filter/FieldsFilter.php
+++ b/src/Filter/FieldsFilter.php
@@ -2,6 +2,8 @@
 
 namespace Paysera\Component\Serializer\Filter;
 
+use ArrayObject;
+
 class FieldsFilter
 {
     /**
@@ -33,7 +35,7 @@ public function filter($data, ?array $fields = null, array $scope = [])
         if ($this->isAssociativeArray($data)) {
             $result = $this->filterByConfig($data, $fieldsConfig);
             if (is_array($result) && count($result) === 0) {
-                $result = new \ArrayObject();
+                $result = new ArrayObject();
             }
             return $result;
         } else {
@@ -52,7 +54,7 @@ public function filter($data, ?array $fields = null, array $scope = [])
      */
     protected function filterByConfig($data, FieldsConfig $fieldsConfig)
     {
-        $result = array();
+        $result = [];
         foreach ($data as $fieldName => $value) {
             if ($fieldsConfig->isIncluded($fieldName)) {
                 if (is_array($value)) {
diff --git a/src/Filter/FieldsParser.php b/src/Filter/FieldsParser.php
index 885c95e..8e5b029 100644
--- a/src/Filter/FieldsParser.php
+++ b/src/Filter/FieldsParser.php
@@ -2,9 +2,10 @@
 
 namespace Paysera\Component\Serializer\Filter;
 
+use InvalidArgumentException;
+
 class FieldsParser
 {
-
     /**
      * @param null|array $fields
      * @param array $scope
@@ -23,7 +24,7 @@ public function parseFields(?array $fields = null, array $scope = [])
     /**
      * @param null|array $fields
      *
-     * @throws \InvalidArgumentException
+     * @throws InvalidArgumentException
      * @return FieldsConfig
      */
     public function parseUnscopedFields(?array $fields = null)
@@ -33,15 +34,15 @@ public function parseUnscopedFields(?array $fields = null)
         }
 
         $defaultsIncluded = false;
-        $includedFields = array();
-        $fieldExtensions = array();
+        $includedFields = [];
+        $fieldExtensions = [];
 
         foreach ($fields as $fieldDefinition) {
             // todo: take curly braces? see commented test-case for possible usage
             foreach (explode(',', $fieldDefinition) as $field) {
                 $list = explode('.', $field, 2);
                 if (isset($list[1]) && $list[1] === '') {
-                    throw new \InvalidArgumentException('Invalid field provided, field cannot end with a dot');
+                    throw new InvalidArgumentException('Invalid field provided, field cannot end with a dot');
                 }
                 $name = $list[0];
                 $extension = isset($list[1]) ? $list[1] : null;
@@ -63,6 +64,6 @@ public function parseUnscopedFields(?array $fields = null)
      */
     protected function createWithDefaultsIncluded()
     {
-        return new FieldsConfig(true, array(), array());
+        return new FieldsConfig(true, [], []);
     }
 }
diff --git a/src/Normalizer/ArrayNormalizer.php b/src/Normalizer/ArrayNormalizer.php
index 244fa72..500b0e2 100644
--- a/src/Normalizer/ArrayNormalizer.php
+++ b/src/Normalizer/ArrayNormalizer.php
@@ -3,6 +3,7 @@
 namespace Paysera\Component\Serializer\Normalizer;
 
 use Paysera\Component\Serializer\Entity\NormalizationContextInterface;
+use Paysera\Component\Serializer\Exception\InvalidDataException;
 
 class ArrayNormalizer implements DenormalizerInterface, ContextAwareNormalizerInterface
 {
@@ -28,11 +29,11 @@ public function __construct($innerMapper)
      *
      * @return mixed
      *
-     * @throws \Paysera\Component\Serializer\Exception\InvalidDataException
+     * @throws InvalidDataException
      */
     public function mapToEntity($data)
     {
-        $result = array();
+        $result = [];
         if ($data !== null) {
             foreach ($data as $innerElement) {
                 $result[] = $this->innerMapper->mapToEntity($innerElement);
@@ -43,7 +44,7 @@ public function mapToEntity($data)
 
     public function mapFromEntity($entity, ?NormalizationContextInterface $context = null)
     {
-        $result = array();
+        $result = [];
         if ($entity !== null) {
             foreach ($entity as $innerElement) {
                 $result[] = $this->innerMapper->mapFromEntity($innerElement, $context);
diff --git a/src/Normalizer/AssociativeArrayNormalizer.php b/src/Normalizer/AssociativeArrayNormalizer.php
index 52c6764..3e25db0 100644
--- a/src/Normalizer/AssociativeArrayNormalizer.php
+++ b/src/Normalizer/AssociativeArrayNormalizer.php
@@ -2,6 +2,8 @@
 
 namespace Paysera\Component\Serializer\Normalizer;
 
+use ArrayObject;
+
 class AssociativeArrayNormalizer implements DenormalizerInterface, NormalizerInterface
 {
     /**
@@ -28,7 +30,7 @@ public function __construct($innerMapper)
      */
     public function mapFromEntity($entity)
     {
-        $result = new \ArrayObject();
+        $result = new ArrayObject();
         if ($entity !== null) {
             foreach ($entity as $key => $innerElement) {
                 $result[$key] = $this->innerMapper->mapFromEntity($innerElement);
@@ -46,7 +48,7 @@ public function mapFromEntity($entity)
      */
     public function mapToEntity($data)
     {
-        $result = array();
+        $result = [];
         if ($data !== null) {
             foreach ($data as $key => $innerElement) {
                 $result[$key] = $this->innerMapper->mapToEntity($innerElement);
diff --git a/src/Normalizer/BaseDenormalizer.php b/src/Normalizer/BaseDenormalizer.php
index bdb67ac..d4f8ebf 100644
--- a/src/Normalizer/BaseDenormalizer.php
+++ b/src/Normalizer/BaseDenormalizer.php
@@ -63,7 +63,7 @@ protected function checkRequiredKeys($data, $requiredKeys)
      *
      * @param $data
      * @param $keys
-     * @throws \Paysera\Component\Serializer\Exception\InvalidDataException
+     * @throws InvalidDataException
      */
     protected function checkOnlyOneKeyExists($data, $keys)
     {
@@ -81,4 +81,4 @@ protected function checkOnlyOneKeyExists($data, $keys)
             }
         }
     }
-} 
+}
diff --git a/src/Normalizer/DateNormalizer.php b/src/Normalizer/DateNormalizer.php
index cd86fac..b148a66 100644
--- a/src/Normalizer/DateNormalizer.php
+++ b/src/Normalizer/DateNormalizer.php
@@ -2,6 +2,8 @@
 
 namespace Paysera\Component\Serializer\Normalizer;
 
+use DateTime;
+use DateTimeZone;
 use Paysera\Component\Serializer\Exception\InvalidDataException;
 
 class DateNormalizer extends BaseDenormalizer implements NormalizerInterface
@@ -12,7 +14,7 @@ class DateNormalizer extends BaseDenormalizer implements NormalizerInterface
     protected $format;
 
     /**
-     * @var \DateTimeZone
+     * @var DateTimeZone
      */
     protected $remoteTimezone;
 
@@ -25,11 +27,15 @@ public function __construct($format, $remoteTimezone = null)
     /**
      * @param string $data
      * @throws InvalidDataException
-     * @return \DateTime
+     * @return DateTime
      */
     public function mapToEntity($data)
     {
-        $date = \DateTime::createFromFormat(
+        if ($data === null) {
+            throw new InvalidDataException('Date must be provided');
+        }
+
+        $date = DateTime::createFromFormat(
             $this->format,
             $data,
             $this->remoteTimezone
@@ -50,7 +56,7 @@ public function mapToEntity($data)
     }
 
     /**
-     * @param \DateTime $entity
+     * @param DateTime $entity
      * @return string
      */
     public function mapFromEntity($entity)
@@ -67,6 +73,6 @@ public function mapFromEntity($entity)
 
     protected function getLocalTimezone()
     {
-        return new \DateTimeZone(date_default_timezone_get());
+        return new DateTimeZone(date_default_timezone_get());
     }
 }
diff --git a/src/Normalizer/DenormalizerInterface.php b/src/Normalizer/DenormalizerInterface.php
index 202a869..23329d8 100644
--- a/src/Normalizer/DenormalizerInterface.php
+++ b/src/Normalizer/DenormalizerInterface.php
@@ -2,6 +2,8 @@
 
 namespace Paysera\Component\Serializer\Normalizer;
 
+use Paysera\Component\Serializer\Exception\InvalidDataException;
+
 interface DenormalizerInterface
 {
     /**
@@ -11,7 +13,7 @@ interface DenormalizerInterface
      *
      * @return mixed
      *
-     * @throws \Paysera\Component\Serializer\Exception\InvalidDataException
+     * @throws InvalidDataException
      */
     public function mapToEntity($data);
 }
diff --git a/src/Normalizer/DistributedNormalizer.php b/src/Normalizer/DistributedNormalizer.php
index 3ace9a2..4ec04c0 100644
--- a/src/Normalizer/DistributedNormalizer.php
+++ b/src/Normalizer/DistributedNormalizer.php
@@ -4,6 +4,7 @@
 
 use Paysera\Component\Serializer\Accessor\FieldAccessorInterface;
 use Paysera\Component\Serializer\Entity\NormalizationContextInterface;
+use Paysera\Component\Serializer\Exception\InvalidDataException;
 use Paysera\Component\Serializer\Factory\ContextAwareNormalizerFactory;
 use Paysera\Component\Serializer\Filter\FieldsFilter;
 use Paysera\Component\Serializer\Filter\FieldsParser;
@@ -16,12 +17,12 @@ class DistributedNormalizer implements DenormalizerInterface, ContextAwareNormal
     protected $factory;
 
     /**
-     * @var \Paysera\Component\Serializer\Filter\FieldsFilter
+     * @var FieldsFilter
      */
     protected $fieldsFilter;
 
     /**
-     * @var \Paysera\Component\Serializer\Filter\FieldsParser
+     * @var FieldsParser
      */
     protected $fieldsParser;
 
@@ -33,23 +34,23 @@ class DistributedNormalizer implements DenormalizerInterface, ContextAwareNormal
     /**
      * @var FieldAccessorInterface[]
      */
-    protected $fieldAccessors = array();
+    protected $fieldAccessors = [];
 
     /**
      * @var array of boolean
      */
-    protected $fieldDefault = array();
+    protected $fieldDefault = [];
 
     /**
      * @var DenormalizerInterface[]|NormalizerInterface[]
      */
-    protected $fieldNormalizers = array();
+    protected $fieldNormalizers = [];
 
     /**
-     * @param \Paysera\Component\Serializer\Factory\ContextAwareNormalizerFactory $factory
-     * @param \Paysera\Component\Serializer\Filter\FieldsParser                   $fieldsParser
-     * @param \Paysera\Component\Serializer\Filter\FieldsFilter                   $fieldsFilter
-     * @param DenormalizerInterface|NormalizerInterface                       $normalizer
+     * @param ContextAwareNormalizerFactory             $factory
+     * @param FieldsParser                              $fieldsParser
+     * @param FieldsFilter                              $fieldsFilter
+     * @param DenormalizerInterface|NormalizerInterface $normalizer
      */
     public function __construct(
         ContextAwareNormalizerFactory $factory,
@@ -97,11 +98,11 @@ public function addAdditionalField($fieldName, FieldAccessorInterface $fieldAcce
      *
      * @return mixed
      *
-     * @throws \Paysera\Component\Serializer\Exception\InvalidDataException
+     * @throws InvalidDataException
      */
     public function mapToEntity($data)
     {
-        $additional = array();
+        $additional = [];
         if (is_array($data)) {
             foreach ($data as $key => $value) {
                 if (
@@ -141,7 +142,7 @@ public function mapFromEntity($entity, ?NormalizationContextInterface $context =
         }
 
         $fields = $context !== null ? $context->getFields() : null;
-        $scope = $context !== null ? $context->getScope() : array();
+        $scope = $context !== null ? $context->getScope() : [];
         $data = $this->fieldsFilter->filter($data, $fields, $scope);
 
         $fieldsConfig = $this->fieldsParser->parseFields($fields, $scope);
diff --git a/src/Normalizer/FilterNormalizer.php b/src/Normalizer/FilterNormalizer.php
index a49abab..87e2b98 100644
--- a/src/Normalizer/FilterNormalizer.php
+++ b/src/Normalizer/FilterNormalizer.php
@@ -11,7 +11,7 @@ class FilterNormalizer extends BaseDenormalizer implements NormalizerInterface
     protected $maxLimit;
     protected $orderByFields;
 
-    public function __construct($orderByFields = array(), $defaultLimit = 20, $maxLimit = 200)
+    public function __construct($orderByFields = [], $defaultLimit = 20, $maxLimit = 200)
     {
         $this->defaultLimit = $defaultLimit;
         $this->maxLimit = $maxLimit;
@@ -25,7 +25,7 @@ public function __construct($orderByFields = array(), $defaultLimit = 20, $maxLi
      *
      * @return mixed
      *
-     * @throws \Paysera\Component\Serializer\Exception\InvalidDataException
+     * @throws InvalidDataException
      */
     public function mapToEntity($data)
     {
@@ -41,7 +41,7 @@ public function mapToEntity($data)
      */
     public function mapFromEntity($entity)
     {
-        $data = array();
+        $data = [];
         if ($entity->getLimit() !== null) {
             $data['limit'] = $entity->getLimit();
         }
@@ -124,7 +124,7 @@ protected function mapBaseKeys($data, Filter $filter)
                 throw new InvalidDataException('order_direction is unsupported for this method');
             }
             $orderDirection = strtoupper($orderDirection);
-            if (!in_array($orderDirection, array('ASC', 'DESC'))) {
+            if (!in_array($orderDirection, ['ASC', 'DESC'])) {
                 throw new InvalidDataException('Invalid order_direction value');
             }
             $filter->setOrderAsc($orderDirection === 'ASC');
diff --git a/src/Normalizer/PlainNormalizer.php b/src/Normalizer/PlainNormalizer.php
index 7a4b288..dbefbae 100644
--- a/src/Normalizer/PlainNormalizer.php
+++ b/src/Normalizer/PlainNormalizer.php
@@ -2,6 +2,8 @@
 
 namespace Paysera\Component\Serializer\Normalizer;
 
+use Paysera\Component\Serializer\Exception\InvalidDataException;
+
 class PlainNormalizer implements NormalizerInterface, DenormalizerInterface
 {
     /**
@@ -23,7 +25,7 @@ public function mapFromEntity($entity)
      *
      * @return mixed
      *
-     * @throws \Paysera\Component\Serializer\Exception\InvalidDataException
+     * @throws InvalidDataException
      */
     public function mapToEntity($data)
     {
diff --git a/src/Normalizer/ResultMetadataNormalizer.php b/src/Normalizer/ResultMetadataNormalizer.php
index 65ff8f9..1791809 100644
--- a/src/Normalizer/ResultMetadataNormalizer.php
+++ b/src/Normalizer/ResultMetadataNormalizer.php
@@ -6,7 +6,6 @@
 
 class ResultMetadataNormalizer implements NormalizerInterface
 {
-
     /**
      * Maps some structure to raw data. Usually entity object to array
      *
@@ -18,10 +17,10 @@ public function mapFromEntity($result)
     {
         $filter = $result->getFilter();
 
-        $data = array(
+        $data = [
             'total' => $result->getTotalCount(),
             'limit' => $filter ? $filter->getLimit() : null,
-        );
+        ];
 
         if ($result->getAfter() !== null) {
             $data['cursors']['after'] = $result->getAfter();
diff --git a/src/Normalizer/ResultNormalizer.php b/src/Normalizer/ResultNormalizer.php
index 729233b..1f62227 100644
--- a/src/Normalizer/ResultNormalizer.php
+++ b/src/Normalizer/ResultNormalizer.php
@@ -5,6 +5,7 @@
 use Paysera\Component\Serializer\Entity\Filter;
 use Paysera\Component\Serializer\Entity\NormalizationContextInterface;
 use Paysera\Component\Serializer\Entity\Result;
+use Paysera\Component\Serializer\Exception\InvalidDataException;
 
 class ResultNormalizer implements ContextAwareNormalizerInterface, DenormalizerInterface
 {
@@ -58,13 +59,13 @@ public function setMetadataNormalizer($metadataNormalizer)
      */
     public function mapFromEntity($entity, ?NormalizationContextInterface $context = null)
     {
-        return array(
+        return [
             $this->itemsKey => $this->mapItemsFromEntity(
                 $entity->getItems(),
                 $context !== null ? $context->createScopedContext($this->itemsKey) : null
             ),
             '_metadata' => $this->mapMetadataFromEntity($entity),
-        );
+        ];
     }
 
     /**
@@ -74,7 +75,7 @@ public function mapFromEntity($entity, ?NormalizationContextInterface $context =
      *
      * @return mixed
      *
-     * @throws \Paysera\Component\Serializer\Exception\InvalidDataException
+     * @throws InvalidDataException
      */
     public function mapToEntity($data)
     {
diff --git a/src/Normalizer/TransformerDenormalizer.php b/src/Normalizer/TransformerDenormalizer.php
index 9e312b1..d0806fe 100644
--- a/src/Normalizer/TransformerDenormalizer.php
+++ b/src/Normalizer/TransformerDenormalizer.php
@@ -2,6 +2,7 @@
 
 namespace Paysera\Component\Serializer\Normalizer;
 
+use Paysera\Component\Serializer\Exception\InvalidDataException;
 use Paysera\Component\Serializer\Transformer\TransformerInterface;
 
 class TransformerDenormalizer implements DenormalizerInterface
@@ -33,7 +34,7 @@ public function __construct(TransformerInterface $transformer, DenormalizerInter
      *
      * @return mixed
      *
-     * @throws \Paysera\Component\Serializer\Exception\InvalidDataException
+     * @throws InvalidDataException
      */
     public function mapToEntity($data)
     {
diff --git a/src/Normalizer/ViolationNormalizer.php b/src/Normalizer/ViolationNormalizer.php
index 9c5d917..780b685 100644
--- a/src/Normalizer/ViolationNormalizer.php
+++ b/src/Normalizer/ViolationNormalizer.php
@@ -37,7 +37,7 @@ public function mapToEntity($data)
      */
     public function mapFromEntity($entity)
     {
-        $data = array();
+        $data = [];
         if ($entity->getCode() !== null) {
             $data['code'] = $entity->getCode();
         }
diff --git a/src/Validation/PropertiesAwareValidator.php b/src/Validation/PropertiesAwareValidator.php
index ba9656c..31a30ef 100644
--- a/src/Validation/PropertiesAwareValidator.php
+++ b/src/Validation/PropertiesAwareValidator.php
@@ -53,8 +53,8 @@ public function validate($entity, $groups = null)
         }
 
         if ($violationList->count() > 0) {
-            $properties = array();
-            $violations = array();
+            $properties = [];
+            $violations = [];
 
             foreach ($violationList as $violation) {
                 $path = $violation->getPropertyPath();
diff --git a/tests/Entity/FilterTest.php b/tests/Entity/FilterTest.php
new file mode 100644
index 0000000..296332d
--- /dev/null
+++ b/tests/Entity/FilterTest.php
@@ -0,0 +1,47 @@
+<?php
+
+namespace Paysera\Component\Serializer\Tests\Entity;
+
+use Paysera\Component\Serializer\Entity\Filter;
+use Paysera\Component\Serializer\Entity\FollowUpFilter;
+use Paysera\Component\Serializer\Tests\Fixtures\OwnConstructorFilter;
+use PHPUnit\Framework\TestCase;
+use ReflectionClass;
+
+class FilterTest extends TestCase
+{
+    public function testOffsetDefaultsToZero()
+    {
+        $this->assertSame(0, (new Filter())->getOffset());
+    }
+
+    public function testOffsetDefaultsToZeroForSubclassNotCallingParentConstructor()
+    {
+        $this->assertSame(0, (new OwnConstructorFilter('done'))->getOffset());
+    }
+
+    public function testOffsetDefaultsToZeroWhenConstructorIsBypassed()
+    {
+        $filter = (new ReflectionClass(Filter::class))->newInstanceWithoutConstructor();
+
+        $this->assertSame(0, $filter->getOffset());
+    }
+
+    public function testGetOffsetReturnsNullWhenCursorIsUsed()
+    {
+        $this->assertNull((new Filter())->setAfter('cursor')->getOffset());
+        $this->assertNull((new Filter())->setBefore('cursor')->getOffset());
+    }
+
+    public function testFollowUpFilterInheritsOffsetDefault()
+    {
+        $filter = (new ReflectionClass(FollowUpFilter::class))->newInstanceWithoutConstructor();
+
+        $this->assertSame(0, $filter->getOffset());
+    }
+
+    public function testFollowUpFilterKeepsConstructorOffset()
+    {
+        $this->assertSame(10, (new FollowUpFilter(5, 10))->getOffset());
+    }
+}
diff --git a/tests/Entity/ResultTest.php b/tests/Entity/ResultTest.php
new file mode 100644
index 0000000..c30d97d
--- /dev/null
+++ b/tests/Entity/ResultTest.php
@@ -0,0 +1,105 @@
+<?php
+
+namespace Paysera\Component\Serializer\Tests\Entity;
+
+use Paysera\Component\Serializer\Entity\Result;
+use Paysera\Component\Serializer\Tests\Fixtures\OwnConstructorFilter;
+use PHPUnit\Framework\TestCase;
+use ReflectionClass;
+use ReflectionMethod;
+use ReturnTypeWillChange;
+
+class ResultTest extends TestCase
+{
+    public function testIterateResultWithoutItems()
+    {
+        $result = new Result();
+
+        $this->assertSame([], iterator_to_array($result));
+    }
+
+    public function testGetItemsReturnsArrayWhenItemsNotSet()
+    {
+        $result = new Result();
+
+        $this->assertSame([], $result->getItems());
+    }
+
+    public function testIterateResultWithItems()
+    {
+        $result = (new Result())->setItems([1, 2, 3]);
+
+        $this->assertSame([1, 2, 3], iterator_to_array($result));
+    }
+
+    public function testAddItemWithoutSettingItemsFirst()
+    {
+        $result = new Result();
+        $result->addItem('a');
+
+        $this->assertSame(['a'], $result->getItems());
+    }
+
+    public function testTotalCountDefaultAppliesWhenConstructorIsBypassed()
+    {
+        $result = (new ReflectionClass(Result::class))->newInstanceWithoutConstructor();
+
+        $this->assertSame(0, $result->getTotalCount());
+    }
+
+    /**
+     * Reflection-based instantiation is how ORM hydration, reflection serializers and
+     * PHPUnit's disableOriginalConstructor() build objects. Pins the defaults to the
+     * property declarations: a constructor assignment would not cover this path.
+     */
+    public function testItemsDefaultAppliesWhenConstructorIsBypassed()
+    {
+        $result = (new ReflectionClass(Result::class))->newInstanceWithoutConstructor();
+
+        $this->assertSame([], $result->getItems());
+        $this->assertSame([], iterator_to_array($result));
+    }
+
+    /**
+     * Filter carries its offset default on the property declaration, so a descendant
+     * that declares its own constructor without calling parent::__construct() still
+     * reports 0 rather than null — which is what keeps this calculation from silently
+     * skipping and reporting a total of 0 for a non-empty result set.
+     */
+    public function testCalculateTotalCountForFilterSubclassNotCallingParentConstructor()
+    {
+        $result = (new Result(new OwnConstructorFilter()))->setItems([1, 2]);
+
+        $this->assertSame(2, $result->calculateTotalCount(2));
+        $this->assertSame(2, $result->getTotalCount());
+    }
+
+    /**
+     * The PHP 8.1 tentative return type notice is emitted when the class is
+     * declared, not when getIterator() is called, so it cannot be caught with an
+     * error handler from inside a test. Assert the declaration instead: either a
+     * native return type or the attribute keeps IteratorAggregate quiet.
+     */
+    public function testGetIteratorSuppressesTentativeReturnTypeDeprecation()
+    {
+        $method = new ReflectionMethod(Result::class, 'getIterator');
+
+        if ($method->hasReturnType()) {
+            $this->assertSame('Traversable', (string)$method->getReturnType());
+            return;
+        }
+
+        if (PHP_VERSION_ID < 80000) {
+            $this->markTestSkipped('Attributes require PHP 8.0; the notice only exists on PHP 8.1+.');
+        }
+
+        $attributes = array_map(
+            function ($attribute) {
+                return $attribute->getName();
+            },
+            $method->getAttributes()
+        );
+
+        $this->assertContains(ReturnTypeWillChange::class, $attributes);
+    }
+}
diff --git a/tests/Filter/FieldsFilterTest.php b/tests/Filter/FieldsFilterTest.php
index 2526e6a..ea57665 100644
--- a/tests/Filter/FieldsFilterTest.php
+++ b/tests/Filter/FieldsFilterTest.php
@@ -2,6 +2,7 @@
 
 namespace Paysera\Component\Serializer\Tests\Filter;
 
+use ArrayObject;
 use Paysera\Component\Serializer\Filter\FieldsFilter;
 use Paysera\Component\Serializer\Filter\FieldsParser;
 use PHPUnit\Framework\TestCase;
@@ -51,258 +52,258 @@ public function testFilterWithScope($data, $fields, $scope, $result)
 
     public function filterProvider()
     {
-        $simple = array(
+        $simple = [
             'key1' => 'value1',
             'key2' => 'value2',
-        );
-        $complex = array(
+        ];
+        $complex = [
             'key1' => 'value1',
             'key2' => 'value2',
-            'key3' => array('value1', 'value2'),
-            'key4' => array('key1' => 'value1', 'key2' => 'value2'),
-        );
+            'key3' => ['value1', 'value2'],
+            'key4' => ['key1' => 'value1', 'key2' => 'value2'],
+        ];
 
-        return array(
-            'Matches everything if * provided' => array(
+        return [
+            'Matches everything if * provided' => [
                 'data' => $simple,
-                'fields' => array('*'),
+                'fields' => ['*'],
                 'result' => $simple,
-            ),
-            'Filters first level data' => array(
+            ],
+            'Filters first level data' => [
                 'data' => $complex,
-                'fields' => array('key1', 'key4', 'key3'),
-                'result' => array(
+                'fields' => ['key1', 'key4', 'key3'],
+                'result' => [
                     'key1' => 'value1',
-                    'key3' => array('value1', 'value2'),
-                    'key4' => array('key1' => 'value1', 'key2' => 'value2'),
-                ),
-            ),
-            'Ignores additional fields if * provided' => array(
+                    'key3' => ['value1', 'value2'],
+                    'key4' => ['key1' => 'value1', 'key2' => 'value2'],
+                ],
+            ],
+            'Ignores additional fields if * provided' => [
                 'data' => $complex,
-                'fields' => array('key1', '*', 'key2'),
+                'fields' => ['key1', '*', 'key2'],
                 'result' => $complex,
-            ),
-            'Filters second level data' => array(
+            ],
+            'Filters second level data' => [
                 'data' => $complex,
-                'fields' => array('key1', 'key3', 'key4.key1'),
-                'result' => array(
+                'fields' => ['key1', 'key3', 'key4.key1'],
+                'result' => [
                     'key1' => 'value1',
-                    'key3' => array('value1', 'value2'),
-                    'key4' => array('key1' => 'value1'),
-                ),
-            ),
-            'Takes subtree if item provided' => array(
+                    'key3' => ['value1', 'value2'],
+                    'key4' => ['key1' => 'value1'],
+                ],
+            ],
+            'Takes subtree if item provided' => [
                 'data' => $complex,
-                'fields' => array('key1', 'key3', 'key4'),
-                'result' => array(
+                'fields' => ['key1', 'key3', 'key4'],
+                'result' => [
                     'key1' => 'value1',
-                    'key3' => array('value1', 'value2'),
-                    'key4' => array('key1' => 'value1', 'key2' => 'value2'),
-                ),
-            ),
-            'Takes subtree if item with * provided' => array(
+                    'key3' => ['value1', 'value2'],
+                    'key4' => ['key1' => 'value1', 'key2' => 'value2'],
+                ],
+            ],
+            'Takes subtree if item with * provided' => [
                 'data' => $complex,
-                'fields' => array('key1', 'key3', 'key4.*', 'key.key2'),
-                'result' => array(
+                'fields' => ['key1', 'key3', 'key4.*', 'key.key2'],
+                'result' => [
                     'key1' => 'value1',
-                    'key3' => array('value1', 'value2'),
-                    'key4' => array('key1' => 'value1', 'key2' => 'value2'),
-                ),
-            ),
-            'Ignores additional fields' => array(
+                    'key3' => ['value1', 'value2'],
+                    'key4' => ['key1' => 'value1', 'key2' => 'value2'],
+                ],
+            ],
+            'Ignores additional fields' => [
                 'data' => $complex,
-                'fields' => array('key1', 'key3', 'key4.*', 'key.key2', 'newkey', 'newkey.a', 'newkey.*', 'key4.new'),
-                'result' => array(
+                'fields' => ['key1', 'key3', 'key4.*', 'key.key2', 'newkey', 'newkey.a', 'newkey.*', 'key4.new'],
+                'result' => [
                     'key1' => 'value1',
-                    'key3' => array('value1', 'value2'),
-                    'key4' => array('key1' => 'value1', 'key2' => 'value2'),
-                ),
-            ),
-            'Do not take with key 0' => array(
-                'data' => array('payments' => array(
-                    '0' => array('id' => 123, 'description' => 'abc1'),
-                    'asd' => array('id' => 124, 'description' => 'abc2'),
-                    'b' => array('id' => 125, 'description' => 'abc3'),
-                )),
-                'fields' => array('payments.asd'),
-                'result' => array('payments' => array(
-                    'asd' => array('id' => 124, 'description' => 'abc2'),
-                )),
-            ),
-            'Takes numeric keys' => array(
-                'data' => array('payments' => array(
-                    '1' => array('id' => 123, 'description' => 'abc1'),
-                    'asd' => array('id' => 124, 'description' => 'abc2'),
-                    'b' => array('id' => 125, 'description' => 'abc3'),
-                )),
-                'fields' => array('payments.1'),
-                'result' => array('payments' => array(
-                    '1' => array('id' => 123, 'description' => 'abc1'),
-                )),
-            ),
-            'Filters for array items' => array(
-                'data' => array('payments' => array(
-                    array('id' => 123, 'description' => 'abc1'),
-                    array('id' => 124, 'description' => 'abc2'),
-                    array('id' => 125, 'description' => 'abc3'),
-                )),
-                'fields' => array('payments.id'),
-                'result' => array('payments' => array(
-                    array('id' => 123),
-                    array('id' => 124),
-                    array('id' => 125),
-                )),
-            ),
-            'Filters for array items at top level' => array(
-                'data' => array(
-                    array('id' => 123, 'description' => 'abc1'),
-                    array('id' => 124, 'description' => 'abc2'),
-                    array('id' => 125, 'description' => 'abc3'),
-                ),
-                'fields' => array('id'),
-                'result' => array(
-                    array('id' => 123),
-                    array('id' => 124),
-                    array('id' => 125),
-                ),
-            ),
-            'Correctly gets associative arrays' => array(
-                'data' => array('payments' => array(
-                    array('id' => 123, 'description' => 'abc1'),
-                    array('id' => 124, 'description' => 'abc2'),
-                    5 => array('id' => 125, 'description' => 'abc3'),
-                )),
-                'fields' => array('payments.id'),
-                'result' => array('payments' => new \ArrayObject()),
-            ),
-            'Takes all fields if wildcard on parent specified' => array(
-                'data' => array('a1' => array('a2' => array('a3' => array('a4' => 'value1', 'a5' => 'value2')))),
-                'fields' => array('*', 'a1.a2.a3.a4'),
-                'result' => array('a1' => array('a2' => array('a3' => array('a4' => 'value1', 'a5' => 'value2')))),
-            ),
-            'Correctly filters deep-nested arrays' => array(
-                'data' => array('a1' => array(
-                    'a2' => array('a3' => array('a4' => 'value1', 'a5' => 'value2'), 'a32' => '1'),
-                )),
-                'fields' => array('a1.a2.a3.a4'),
-                'result' => array('a1' => array('a2' => array('a3' => array('a4' => 'value1')))),
-            ),
-            'Takes keys from second level arrays' => array(
-                'data' => array('scalar' => 'asd', 'array' => array(
-                    array('item1' => 'asd', 'item2' => 'qwe', 'item3' => array('a', 'b')),
-                    array('item1' => 'qwe', 'item2' => 'rty', 'item3' => array('c', 'd')),
-                    array('item1' => 'fgh', 'item2' => 'yui', 'item3' => array('e', 'f')),
-                )),
-                'fields' => array('array.item1', 'array.item3'),
-                'result' => array('array' => array(
-                    array('item1' => 'asd', 'item3' => array('a', 'b')),
-                    array('item1' => 'qwe', 'item3' => array('c', 'd')),
-                    array('item1' => 'fgh', 'item3' => array('e', 'f')),
-                )),
-            ),
-            'Takes several fields from one item' => array(
-                'data' => array('a1' => '1', 'a2' => '2', 'a3' => '3', 'a4' => '4'),
-                'fields' => array('a1,a4', 'a2'),
-                'result' => array('a1' => '1', 'a2' => '2', 'a4' => '4'),
-            ),
-            'Leaves curly braces if all items are filtered' => array(
-                'data' => array('a1' => '1', 'a2' => '2', 'a3' => '3', 'a4' => '4'),
-                'fields' => array('b1'),
-                'result' => new \ArrayObject(),
-            ),
-            'Leaves simple array if all items are filtered' => array(
-                'data' => array('a1' => array('a', 'b', 'c')),
-                'fields' => array('a1.b1'),
-                'result' => array('a1' => array('a', 'b', 'c')),
-            ),
+                    'key3' => ['value1', 'value2'],
+                    'key4' => ['key1' => 'value1', 'key2' => 'value2'],
+                ],
+            ],
+            'Do not take with key 0' => [
+                'data' => ['payments' => [
+                    '0' => ['id' => 123, 'description' => 'abc1'],
+                    'asd' => ['id' => 124, 'description' => 'abc2'],
+                    'b' => ['id' => 125, 'description' => 'abc3'],
+                ]],
+                'fields' => ['payments.asd'],
+                'result' => ['payments' => [
+                    'asd' => ['id' => 124, 'description' => 'abc2'],
+                ]],
+            ],
+            'Takes numeric keys' => [
+                'data' => ['payments' => [
+                    '1' => ['id' => 123, 'description' => 'abc1'],
+                    'asd' => ['id' => 124, 'description' => 'abc2'],
+                    'b' => ['id' => 125, 'description' => 'abc3'],
+                ]],
+                'fields' => ['payments.1'],
+                'result' => ['payments' => [
+                    '1' => ['id' => 123, 'description' => 'abc1'],
+                ]],
+            ],
+            'Filters for array items' => [
+                'data' => ['payments' => [
+                    ['id' => 123, 'description' => 'abc1'],
+                    ['id' => 124, 'description' => 'abc2'],
+                    ['id' => 125, 'description' => 'abc3'],
+                ]],
+                'fields' => ['payments.id'],
+                'result' => ['payments' => [
+                    ['id' => 123],
+                    ['id' => 124],
+                    ['id' => 125],
+                ]],
+            ],
+            'Filters for array items at top level' => [
+                'data' => [
+                    ['id' => 123, 'description' => 'abc1'],
+                    ['id' => 124, 'description' => 'abc2'],
+                    ['id' => 125, 'description' => 'abc3'],
+                ],
+                'fields' => ['id'],
+                'result' => [
+                    ['id' => 123],
+                    ['id' => 124],
+                    ['id' => 125],
+                ],
+            ],
+            'Correctly gets associative arrays' => [
+                'data' => ['payments' => [
+                    ['id' => 123, 'description' => 'abc1'],
+                    ['id' => 124, 'description' => 'abc2'],
+                    5 => ['id' => 125, 'description' => 'abc3'],
+                ]],
+                'fields' => ['payments.id'],
+                'result' => ['payments' => new ArrayObject()],
+            ],
+            'Takes all fields if wildcard on parent specified' => [
+                'data' => ['a1' => ['a2' => ['a3' => ['a4' => 'value1', 'a5' => 'value2']]]],
+                'fields' => ['*', 'a1.a2.a3.a4'],
+                'result' => ['a1' => ['a2' => ['a3' => ['a4' => 'value1', 'a5' => 'value2']]]],
+            ],
+            'Correctly filters deep-nested arrays' => [
+                'data' => ['a1' => [
+                    'a2' => ['a3' => ['a4' => 'value1', 'a5' => 'value2'], 'a32' => '1'],
+                ]],
+                'fields' => ['a1.a2.a3.a4'],
+                'result' => ['a1' => ['a2' => ['a3' => ['a4' => 'value1']]]],
+            ],
+            'Takes keys from second level arrays' => [
+                'data' => ['scalar' => 'asd', 'array' => [
+                    ['item1' => 'asd', 'item2' => 'qwe', 'item3' => ['a', 'b']],
+                    ['item1' => 'qwe', 'item2' => 'rty', 'item3' => ['c', 'd']],
+                    ['item1' => 'fgh', 'item2' => 'yui', 'item3' => ['e', 'f']],
+                ]],
+                'fields' => ['array.item1', 'array.item3'],
+                'result' => ['array' => [
+                    ['item1' => 'asd', 'item3' => ['a', 'b']],
+                    ['item1' => 'qwe', 'item3' => ['c', 'd']],
+                    ['item1' => 'fgh', 'item3' => ['e', 'f']],
+                ]],
+            ],
+            'Takes several fields from one item' => [
+                'data' => ['a1' => '1', 'a2' => '2', 'a3' => '3', 'a4' => '4'],
+                'fields' => ['a1,a4', 'a2'],
+                'result' => ['a1' => '1', 'a2' => '2', 'a4' => '4'],
+            ],
+            'Leaves curly braces if all items are filtered' => [
+                'data' => ['a1' => '1', 'a2' => '2', 'a3' => '3', 'a4' => '4'],
+                'fields' => ['b1'],
+                'result' => new ArrayObject(),
+            ],
+            'Leaves simple array if all items are filtered' => [
+                'data' => ['a1' => ['a', 'b', 'c']],
+                'fields' => ['a1.b1'],
+                'result' => ['a1' => ['a', 'b', 'c']],
+            ],
             // todo:
-//            'Takes curly braces' => array(
-//                'data' => array('a1' => '1', 'a2' => '2', 'a3' => array(
+//            'Takes curly braces' => [
+//                'data' => ['a1' => '1', 'a2' => '2', 'a3' => [
 //                    'a31' => '31',
 //                    'a32' => '32',
-//                    'a33' => array(
-//                        array('a331' => '331a', 'a332' => '332a', 'a333' => '333a', 'a334' => '334a'),
-//                        array('a331' => '331b', 'a332' => '332b', 'a333' => '333b', 'a334' => '334a'),
-//                        array('a331' => '331c', 'a332' => '332c', 'a333' => '333c', 'a334' => '334a'),
-//                    ),
-//                ), 'a4' => '4'),
-//                'fields' => array('a3.{a31,a33.a331,a33.{a333}}', '{a1,a4},a3.a33.a334'),
-//                'result' => array('a1' => '1', 'a3' => array(
+//                    'a33' => [
+//                        ['a331' => '331a', 'a332' => '332a', 'a333' => '333a', 'a334' => '334a'],
+//                        ['a331' => '331b', 'a332' => '332b', 'a333' => '333b', 'a334' => '334a'],
+//                        ['a331' => '331c', 'a332' => '332c', 'a333' => '333c', 'a334' => '334a'],
+//                    ],
+//                ], 'a4' => '4'],
+//                'fields' => ['a3.{a31,a33.a331,a33.{a333}}', '{a1,a4},a3.a33.a334'],
+//                'result' => ['a1' => '1', 'a3' => [
 //                    'a31' => '31',
-//                    'a33' => array(
-//                        array('a331' => '331a', 'a333' => '333a', 'a334' => '334a'),
-//                        array('a331' => '331b', 'a333' => '333b', 'a334' => '334a'),
-//                        array('a331' => '331c', 'a333' => '333c', 'a334' => '334a'),
-//                    ),
-//                ), 'a4' => '4'),
-//            ),
-        );
+//                    'a33' => [
+//                        ['a331' => '331a', 'a333' => '333a', 'a334' => '334a'],
+//                        ['a331' => '331b', 'a333' => '333b', 'a334' => '334a'],
+//                        ['a331' => '331c', 'a333' => '333c', 'a334' => '334a'],
+//                    ],
+//                ], 'a4' => '4'],
+//            ],
+        ];
     }
 
     public function filterWithScopeProvider()
     {
-        $simple = array(
+        $simple = [
             'key1' => 'value1',
             'key2' => 'value2',
-        );
-        $complex = array(
+        ];
+        $complex = [
             'key1' => 'value1',
             'key2' => 'value2',
-            'key3' => array('value1', 'value2'),
-            'key4' => array('key1' => 'value1', 'key2' => 'value2'),
-        );
+            'key3' => ['value1', 'value2'],
+            'key4' => ['key1' => 'value1', 'key2' => 'value2'],
+        ];
 
-        return array(
-            'Matches everything if * provided' => array(
+        return [
+            'Matches everything if * provided' => [
                 'data' => $simple,
-                'fields' => array('*'),
-                'scope' => array('scope'),
+                'fields' => ['*'],
+                'scope' => ['scope'],
                 'result' => $simple,
-            ),
-            'Filters second level data' => array(
+            ],
+            'Filters second level data' => [
                 'data' => $complex,
-                'fields' => array('key0.key1', 'key0.key3', 'key0.key4.key1'),
-                'scope' => array('key0'),
-                'result' => array(
+                'fields' => ['key0.key1', 'key0.key3', 'key0.key4.key1'],
+                'scope' => ['key0'],
+                'result' => [
                     'key1' => 'value1',
-                    'key3' => array('value1', 'value2'),
-                    'key4' => array('key1' => 'value1'),
-                ),
-            ),
-            'Correctly gets associative arrays' => array(
-                'data' => array('payments' => array(
-                    array('id' => 123, 'description' => 'abc1'),
-                    array('id' => 124, 'description' => 'abc2'),
-                    5 => array('id' => 125, 'description' => 'abc3'),
-                )),
-                'fields' => array('scope.payments.id'),
-                'scope' => array('scope'),
-                'result' => array('payments' => new \ArrayObject()),
-            ),
-            'Takes all fields if wildcard on parent specified' => array(
-                'data' => array('a1' => array('a2' => array('a3' => array('a4' => 'value1', 'a5' => 'value2')))),
-                'fields' => array('*', 'scope.a1.a2.a3.a4'),
-                'scope' => array('scope'),
-                'result' => array('a1' => array('a2' => array('a3' => array('a4' => 'value1', 'a5' => 'value2')))),
-            ),
-            'Ignores other fields' => array(
-                'data' => array('a1' => array('a2' => array('a3' => array('a4' => 'value1', 'a5' => 'value2')))),
-                'fields' => array('a0.a1.a2.a3.a4', 'aa.a1.a2.a3.a5'),
-                'scope' => array('a0'),
-                'result' => array('a1' => array('a2' => array('a3' => array('a4' => 'value1')))),
-            ),
-            'Takes nested scope' => array(
-                'data' => array(array('a4' => 'value1', 'a5' => 'value2')),
-                'fields' => array('a0.a1.a2.a3.a4', 'aa.a1.a2.a3.a5'),
-                'scope' => array('a0', 'a1', 'a2', 'a3'),
-                'result' => array(array('a4' => 'value1')),
-            ),
-            'Filters if on another branch' => array(
-                'data' => array(array('a4' => 'value1', 'a5' => 'value2')),
-                'fields' => array('a1.a2'),
-                'scope' => array('a2'),
-                'result' => array(array()),
-            ),
-        );
+                    'key3' => ['value1', 'value2'],
+                    'key4' => ['key1' => 'value1'],
+                ],
+            ],
+            'Correctly gets associative arrays' => [
+                'data' => ['payments' => [
+                    ['id' => 123, 'description' => 'abc1'],
+                    ['id' => 124, 'description' => 'abc2'],
+                    5 => ['id' => 125, 'description' => 'abc3'],
+                ]],
+                'fields' => ['scope.payments.id'],
+                'scope' => ['scope'],
+                'result' => ['payments' => new ArrayObject()],
+            ],
+            'Takes all fields if wildcard on parent specified' => [
+                'data' => ['a1' => ['a2' => ['a3' => ['a4' => 'value1', 'a5' => 'value2']]]],
+                'fields' => ['*', 'scope.a1.a2.a3.a4'],
+                'scope' => ['scope'],
+                'result' => ['a1' => ['a2' => ['a3' => ['a4' => 'value1', 'a5' => 'value2']]]],
+            ],
+            'Ignores other fields' => [
+                'data' => ['a1' => ['a2' => ['a3' => ['a4' => 'value1', 'a5' => 'value2']]]],
+                'fields' => ['a0.a1.a2.a3.a4', 'aa.a1.a2.a3.a5'],
+                'scope' => ['a0'],
+                'result' => ['a1' => ['a2' => ['a3' => ['a4' => 'value1']]]],
+            ],
+            'Takes nested scope' => [
+                'data' => [['a4' => 'value1', 'a5' => 'value2']],
+                'fields' => ['a0.a1.a2.a3.a4', 'aa.a1.a2.a3.a5'],
+                'scope' => ['a0', 'a1', 'a2', 'a3'],
+                'result' => [['a4' => 'value1']],
+            ],
+            'Filters if on another branch' => [
+                'data' => [['a4' => 'value1', 'a5' => 'value2']],
+                'fields' => ['a1.a2'],
+                'scope' => ['a2'],
+                'result' => [[]],
+            ],
+        ];
     }
 }
diff --git a/tests/Fixtures/OwnConstructorFilter.php b/tests/Fixtures/OwnConstructorFilter.php
new file mode 100644
index 0000000..e6d02ce
--- /dev/null
+++ b/tests/Fixtures/OwnConstructorFilter.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace Paysera\Component\Serializer\Tests\Fixtures;
+
+use Paysera\Component\Serializer\Entity\Filter;
+
+/**
+ * Filter has no constructor and is designed for subclassing, so descendants are
+ * not obliged to call parent::__construct(). Pins that contract down: the offset
+ * default has to live on the property declaration for this to keep working.
+ */
+class OwnConstructorFilter extends Filter
+{
+    /**
+     * @var string|null
+     */
+    protected $status;
+
+    public function __construct($status = null)
+    {
+        $this->status = $status;
+    }
+}
diff --git a/tests/Normalizer/DateNormalizerTest.php b/tests/Normalizer/DateNormalizerTest.php
index 51b7abc..695739f 100644
--- a/tests/Normalizer/DateNormalizerTest.php
+++ b/tests/Normalizer/DateNormalizerTest.php
@@ -2,6 +2,8 @@
 
 namespace Paysera\Component\Serializer\Tests\Normalizer;
 
+use DateTime;
+use DateTimeZone;
 use Paysera\Component\Serializer\Exception\InvalidDataException;
 use Paysera\Component\Serializer\Normalizer\DateNormalizer;
 use PHPUnit\Framework\TestCase;
@@ -19,28 +21,28 @@ public function testMapToEntity_when_no_correction_by_timezone_needed_then_date_
         $service = new DateNormalizer('Y-m-d H:i:s');
 
         $result = $service->mapToEntity('2013-02-01 12:00:00');
-        $this->assertEquals(new \DateTime('2013-02-01 12:00:00', new \DateTimeZone('Etc/GMT-2')),  $result);
+        $this->assertEquals(new DateTime('2013-02-01 12:00:00', new DateTimeZone('Etc/GMT-2')),  $result);
 
-        $result = $service->mapFromEntity(new \DateTime('2013-02-01 12:00:00'));
+        $result = $service->mapFromEntity(new DateTime('2013-02-01 12:00:00'));
         $this->assertEquals('2013-02-01 12:00:00',  $result);
     }
 
     public function testMapToEntity_when_correction_by_timezone_needed_then_date_modified()
     {
-        $service = new DateNormalizer('Y-m-d H:i:s', new \DateTimeZone('Etc/GMT+0'));
+        $service = new DateNormalizer('Y-m-d H:i:s', new DateTimeZone('Etc/GMT+0'));
 
         $result = $service->mapToEntity('2013-02-01 12:00:00');
-        $this->assertEquals(new \DateTime('2013-02-01 14:00:00'),  $result);
+        $this->assertEquals(new DateTime('2013-02-01 14:00:00'),  $result);
 
-        $result = $service->mapFromEntity(new \DateTime('2013-02-01 14:00:00'));
+        $result = $service->mapFromEntity(new DateTime('2013-02-01 14:00:00'));
         $this->assertEquals('2013-02-01 12:00:00',  $result);
     }
 
     public function testMapToEntity_original_entity_not_modified_when_mapping_from_entity()
     {
-        $service = new DateNormalizer('Y-m-d H:i:s', new \DateTimeZone('Etc/GMT+0'));
+        $service = new DateNormalizer('Y-m-d H:i:s', new DateTimeZone('Etc/GMT+0'));
 
-        $datetimeOriginal = new \DateTime('2013-02-01 14:00:00');
+        $datetimeOriginal = new DateTime('2013-02-01 14:00:00');
         $datetime = clone $datetimeOriginal;
         $service->mapFromEntity($datetime);
 
@@ -49,7 +51,7 @@ public function testMapToEntity_original_entity_not_modified_when_mapping_from_e
 
     public function testMapToEntity_mapping_from_null_entity_returns_null()
     {
-        $service = new DateNormalizer('Y-m-d H:i:s', new \DateTimeZone('Etc/GMT+0'));
+        $service = new DateNormalizer('Y-m-d H:i:s', new DateTimeZone('Etc/GMT+0'));
 
         $datetime = null;
         $result = $service->mapFromEntity($datetime);
@@ -59,10 +61,35 @@ public function testMapToEntity_mapping_from_null_entity_returns_null()
 
     public function testMapToEntity_invalid_date_throws_exception()
     {
-        $service = new DateNormalizer('Y-m-d H:i:s', new \DateTimeZone('Etc/GMT+0'));
+        $service = new DateNormalizer('Y-m-d H:i:s', new DateTimeZone('Etc/GMT+0'));
 
         $datetime = null;
         $this->expectException(InvalidDataException::class);
         $service->mapToEntity('2013-02-31 12:00:00');
     }
+
+    public function testMapToEntity_null_date_throws_exception_without_deprecation()
+    {
+        $service = new DateNormalizer('Y-m-d H:i:s', new DateTimeZone('Etc/GMT+0'));
+
+        $deprecations = [];
+        set_error_handler(
+            function ($errno, $errstr) use (&$deprecations) {
+                $deprecations[] = $errstr;
+                return true;
+            },
+            E_DEPRECATED
+        );
+
+        try {
+            $service->mapToEntity(null);
+            $this->fail('Expected InvalidDataException to be thrown');
+        } catch (InvalidDataException $exception) {
+            $this->assertSame('Date must be provided', $exception->getMessage());
+        } finally {
+            restore_error_handler();
+        }
+
+        $this->assertSame([], $deprecations);
+    }
 }
diff --git a/tests/Normalizer/DistributedNormalizerTest.php b/tests/Normalizer/DistributedNormalizerTest.php
new file mode 100644
index 0000000..700a506
--- /dev/null
+++ b/tests/Normalizer/DistributedNormalizerTest.php
@@ -0,0 +1,42 @@
+<?php
+
+namespace Paysera\Component\Serializer\Tests\Normalizer;
+
+use Paysera\Component\Serializer\Normalizer\DistributedNormalizer;
+use PHPUnit\Framework\TestCase;
+use ReflectionClass;
+use ReflectionProperty;
+
+class DistributedNormalizerTest extends TestCase
+{
+    /**
+     * The three field maps default on the property declarations rather than in the
+     * constructor, so they survive every instantiation path. A constructor assignment
+     * would leave them null for instances built without one — doubles created with
+     * disableOriginalConstructor(), or reflection hydration. Both readers degrade
+     * silently on null rather than throwing: mapFromEntity() iterates $fieldAccessors,
+     * which warns and skips, dropping every distributed field from the output, and
+     * mapToEntity() probes isset($this->fieldNormalizers[$key]), which is simply false
+     * for every key.
+     *
+     * @dataProvider fieldMapProvider
+     */
+    public function testFieldMapsDefaultToArrayWhenConstructorIsBypassed($property)
+    {
+        $normalizer = (new ReflectionClass(DistributedNormalizer::class))->newInstanceWithoutConstructor();
+
+        $reflectionProperty = new ReflectionProperty(DistributedNormalizer::class, $property);
+        $reflectionProperty->setAccessible(true);
+
+        $this->assertSame([], $reflectionProperty->getValue($normalizer));
+    }
+
+    public function fieldMapProvider()
+    {
+        return [
+            'fieldAccessors' => ['fieldAccessors'],
+            'fieldDefault' => ['fieldDefault'],
+            'fieldNormalizers' => ['fieldNormalizers'],
+        ];
+    }
+}