diff --git a/examples/atomic_operations_extension.php b/examples/atomic_operations_extension.php
index caa6aaae..0ecc92a9 100644
--- a/examples/atomic_operations_extension.php
+++ b/examples/atomic_operations_extension.php
@@ -5,7 +5,7 @@
 use alsvanzelf\jsonapi\objects\ResourceObject;
 use alsvanzelf\jsonapi\extensions\AtomicOperationsDocument;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * use the atomic operations extension as extension to the document
diff --git a/examples/bootstrap_examples.php b/examples/bootstrap_examples.php
index acf810cc..6de38497 100644
--- a/examples/bootstrap_examples.php
+++ b/examples/bootstrap_examples.php
@@ -10,7 +10,6 @@
 use alsvanzelf\jsonapi\interfaces\ProfileInterface;
 use alsvanzelf\jsonapi\interfaces\ResourceInterface;
 use alsvanzelf\jsonapi\objects\ResourceIdentifierObject;
-use alsvanzelf\jsonapi\objects\ResourceObject;
 
 ini_set('display_errors', 1);
 error_reporting(-1);
@@ -18,7 +17,8 @@
 require_once __DIR__.'/../vendor/autoload.php';
 
 class ExampleDataset {
-	private static $records = [
+	/** @var array<string, array<int, array<string, string|int>>> */
+	private static array $records = [
 		'articles' => [
 			1 => [
 				'title'    => 'JSON:API paints my bikeshed!',
@@ -58,34 +58,43 @@ class ExampleDataset {
 		],
 	];
 	
-	public static function getRecord($type, $id) {
-		if (!isset(self::$records[$type][$id])) {
+	/**
+	 * @return array<string, string|int>
+	 */
+	public static function getRecord(string $type, int $id): array {
+		if (isset(self::$records[$type][$id]) === false) {
 			throw new \Exception('sorry, we have a limited dataset');
 		}
 		
 		return self::$records[$type][$id];
 	}
 	
-	public static function getEntity($type, $id) {
+	public static function getEntity(string $type, int $id): ExampleUser {
 		$record = self::getRecord($type, $id);
 		
 		$user = new ExampleUser($id);
 		foreach ($record as $key => $value) {
-			$user->$key = $value;
+			$user->$key = $value; // @phpstan-ignore property.dynamicName
 		}
 		
 		return $user;
 	}
 	
-	public static function findRecords($type) {
+	/**
+	 * @return array<array<string, string|int>>
+	 */
+	public static function findRecords(string $type): array {
 		return self::$records[$type];
 	}
 	
-	public static function findEntities($type) {
-		$records  = self::findRecords($type);
-		$entities = [];
+	/**
+	 * @return ExampleUser[]
+	 */
+	public static function findEntities(string $type): array {
+		$recordIds = array_keys(self::findRecords($type));
+		$entities  = [];
 		
-		foreach ($records as $id => $record) {
+		foreach ($recordIds as $id) {
 			$entities[$id] = self::getEntity($type, $id);
 		}
 		
@@ -94,15 +103,15 @@ public static function findEntities($type) {
 }
 
 class ExampleUser {
-	public $name;
-	public $heads;
-	public $unknown;
+	public ?string $name = null;
+	public null|int|string $heads = null;
+	public mixed $unknown = null;
 	
 	public function __construct(
-		public $id,
+		public int $id,
 	) {}
 	
-	function getCurrentLocation() {
+	public function getCurrentLocation(): string {
 		return 'Earth';
 	}
 }
@@ -124,11 +133,7 @@ public function getNamespace(): string {
 	 * optionally helpers for the specific extension
 	 */
 	
-	public function setVersion(ResourceInterface $resource, $version) {
-		if ($resource instanceof HasExtensionMembersInterface === false) {
-			throw new \Exception('resource doesn\'t have extension members');
-		}
-		
+	public function setVersion(ResourceInterface & HasExtensionMembersInterface $resource, string $version): void {
 		if ($resource instanceof ResourceDocument) {
 			$resource->getResource()->addExtensionMember($this, 'id', $version);
 		}
@@ -151,14 +156,11 @@ public function getOfficialLink(): string {
 	 * optionally helpers for the specific profile
 	 */
 	
-	/**
-	 * @param ResourceInterface&HasAttributesInterface $resource
-	 */
-	public function setTimestamps(ResourceInterface $resource, ?\DateTimeInterface $created=null, ?\DateTimeInterface $updated=null) {
-		if ($resource instanceof HasAttributesInterface === false) {
-			throw new \Exception('cannot add attributes to identifier objects');
-		}
-		
+	public function setTimestamps(
+		ResourceInterface & HasAttributesInterface $resource,
+		?\DateTimeInterface $created=null,
+		?\DateTimeInterface $updated=null,
+	): void {
 		$timestamps = [];
 		if ($created !== null) {
 			$timestamps['created'] = $created->format(\DateTime::ISO8601);
diff --git a/examples/collection.php b/examples/collection.php
index cdd5a38c..7041a2a2 100644
--- a/examples/collection.php
+++ b/examples/collection.php
@@ -5,7 +5,7 @@
 use alsvanzelf\jsonapi\CollectionDocument;
 use alsvanzelf\jsonapi\objects\ResourceObject;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 $users = ExampleDataset::findEntities('user');
 
@@ -18,7 +18,7 @@
 foreach ($users as $user) {
 	$resource = ResourceObject::fromObject($user, type: 'user', id: $user->id);
 	
-	if ($user->id == 42) {
+	if ($user->id === 42) {
 		$ship = new ResourceObject('ship', 5);
 		$ship->add('name', 'Heart of Gold');
 		$resource->addRelationship('ship', $ship);
diff --git a/examples/collection_canonical.php b/examples/collection_canonical.php
index a29cb295..82fba06b 100644
--- a/examples/collection_canonical.php
+++ b/examples/collection_canonical.php
@@ -5,7 +5,7 @@
 use alsvanzelf\jsonapi\CollectionDocument;
 use alsvanzelf\jsonapi\objects\ResourceObject;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 $articleRecords = ExampleDataset::findRecords('articles');
 $commentRecords = ExampleDataset::findRecords('comments');
diff --git a/examples/cursor_pagination_profile.php b/examples/cursor_pagination_profile.php
index 5ad180fb..01b7e5e0 100644
--- a/examples/cursor_pagination_profile.php
+++ b/examples/cursor_pagination_profile.php
@@ -6,7 +6,7 @@
 use alsvanzelf\jsonapi\objects\ResourceObject;
 use alsvanzelf\jsonapi\profiles\CursorPaginationProfile;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * use the cursor pagination profile as extension to the document
diff --git a/examples/errors_all_options.php b/examples/errors_all_options.php
index 0174599f..7c14e85b 100644
--- a/examples/errors_all_options.php
+++ b/examples/errors_all_options.php
@@ -5,7 +5,7 @@
 use alsvanzelf\jsonapi\ErrorsDocument;
 use alsvanzelf\jsonapi\objects\ErrorObject;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * setting all options
diff --git a/examples/errors_exception_native.php b/examples/errors_exception_native.php
index 9f2b4058..5cc78803 100644
--- a/examples/errors_exception_native.php
+++ b/examples/errors_exception_native.php
@@ -4,7 +4,7 @@
 
 use alsvanzelf\jsonapi\ErrorsDocument;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * via an exception
@@ -17,12 +17,12 @@
 try {
 	throw new \Exception('unknown user', 404);
 }
-catch (Exception $e) {
+catch (Exception $exception) {
 	$options = [
 		'includeExceptionTrace'    => true,
 		'includeExceptionPrevious' => true,
 	];
-	$document = ErrorsDocument::fromException($e, $options);
+	$document = ErrorsDocument::fromException($exception, $options);
 	
 	$options = [
 		'prettyPrint' => true,
diff --git a/examples/extension.php b/examples/extension.php
index 3ecf4ddb..716e13ae 100644
--- a/examples/extension.php
+++ b/examples/extension.php
@@ -6,7 +6,7 @@
 use alsvanzelf\jsonapi\enums\ContentTypeEnum;
 use alsvanzelf\jsonapi\helpers\Converter;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * use an extension extend the document with new members
diff --git a/examples/meta_only.php b/examples/meta_only.php
index 60562d7f..83c96a1f 100644
--- a/examples/meta_only.php
+++ b/examples/meta_only.php
@@ -4,7 +4,7 @@
 
 use alsvanzelf\jsonapi\MetaDocument;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * there are a few use-cases for sending meta-only responses
diff --git a/examples/null_values.php b/examples/null_values.php
index 4a7cd92c..3c1ac14d 100644
--- a/examples/null_values.php
+++ b/examples/null_values.php
@@ -7,7 +7,7 @@
 use alsvanzelf\jsonapi\objects\LinkObject;
 use alsvanzelf\jsonapi\objects\RelationshipObject;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * tell that a value is non-existing
diff --git a/examples/output.php b/examples/output.php
index 1cb9d4ab..4cd9e133 100644
--- a/examples/output.php
+++ b/examples/output.php
@@ -5,7 +5,7 @@
 use alsvanzelf\jsonapi\MetaDocument;
 use alsvanzelf\jsonapi\enums\ContentTypeEnum;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 $document = new MetaDocument();
 $document->add('foo', 'bar');
@@ -69,10 +69,6 @@
  * send json response
  */
 
-$options = ['prettyPrint' => true, 'contentType' => 'text/html'];
 echo '<h2>Send json response</h2>';
 echo '<pre style="font-size: large;">$document->sendResponse();</pre>';
-echo '<pre>';
-$document->sendResponse($options);
-echo '</pre>';
-echo '<p><em>Also sends http status code ('.$document->getHttpStatusCode().') and headers: [Content-Type: '.ContentTypeEnum::Official->value.']</em></p>';
+echo '<p><em>Echo\'s the result of <code style="font-size: large;">$document->toJson()</code> and sends http status code ('.$document->getHttpStatusCode().') and headers: [Content-Type: '.ContentTypeEnum::Official->value.']</em></p>';
diff --git a/examples/profile.php b/examples/profile.php
index 5bce8471..fe1d64fb 100644
--- a/examples/profile.php
+++ b/examples/profile.php
@@ -6,7 +6,7 @@
 use alsvanzelf\jsonapi\enums\ContentTypeEnum;
 use alsvanzelf\jsonapi\helpers\Converter;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * use a profile to define rules for members
diff --git a/examples/relationship_to_many_document.php b/examples/relationship_to_many_document.php
index f2a2af2a..d199bf1d 100644
--- a/examples/relationship_to_many_document.php
+++ b/examples/relationship_to_many_document.php
@@ -4,7 +4,7 @@
 
 use alsvanzelf\jsonapi\CollectionDocument;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * a to-many relationship response
diff --git a/examples/relationship_to_one_document.php b/examples/relationship_to_one_document.php
index a715ea64..a6584609 100644
--- a/examples/relationship_to_one_document.php
+++ b/examples/relationship_to_one_document.php
@@ -5,7 +5,7 @@
 use alsvanzelf\jsonapi\ResourceDocument;
 use alsvanzelf\jsonapi\enums\DocumentLevelEnum;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * a to-one relationship response
diff --git a/examples/relationships.php b/examples/relationships.php
index 73db5dc8..235a174e 100644
--- a/examples/relationships.php
+++ b/examples/relationships.php
@@ -8,7 +8,7 @@
 use alsvanzelf\jsonapi\objects\RelationshipObject;
 use alsvanzelf\jsonapi\objects\ResourceObject;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * the different ways of adding relationships to a resource
@@ -74,15 +74,6 @@
 
 $document->addRelationshipObject('one-by-one-neighbours', $relationshipObject);
 
-/**
- * custom
- */
-$jsonapi = new ResourceDocument('user', 1);
-$customRelation = [
-	'data' => ['cus' => 'tom'],
-];
-$jsonapi->addRelationship('custom', $customRelation);
-
 /**
  * sending the response
  */
diff --git a/examples/request_superglobals.php b/examples/request_superglobals.php
index cb93d06f..e4a0be9a 100644
--- a/examples/request_superglobals.php
+++ b/examples/request_superglobals.php
@@ -5,7 +5,7 @@
 use alsvanzelf\jsonapi\enums\ContentTypeEnum;
 use alsvanzelf\jsonapi\helpers\RequestParser;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * preparing request data in superglobals from a webserver
@@ -60,31 +60,55 @@
  */
 
 // useful for filling a self link in responses
-var_dump($requestParser->getSelfLink());
+echo '<h2>Get self link</h2>';
+echo '<pre style="font-size: large;">$requestParser->getSelfLink()</pre>';
+echo '<pre>'.var_export($requestParser->getSelfLink(), return: true).'</pre>';
 
 // useful for determining how to process the request (list/get/create/update)
-var_dump($requestParser->hasIncludePaths());
-var_dump($requestParser->hasSparseFieldset('user'));
-var_dump($requestParser->hasSortFields());
-var_dump($requestParser->hasPagination());
-var_dump($requestParser->hasFilter());
+echo '<h2>Check query parameters</h2>';
+echo '<pre style="font-size: large;">$requestParser->hasIncludePaths()</pre>';
+echo '<pre>'.var_export($requestParser->hasIncludePaths(), return: true).'</pre>';
+echo '<pre style="font-size: large;">$requestParser->hasSparseFieldset()</pre>';
+echo '<pre>'.var_export($requestParser->hasSparseFieldset('user'), return: true).'</pre>';
+echo '<pre style="font-size: large;">$requestParser->hasSortFields()</pre>';
+echo '<pre>'.var_export($requestParser->hasSortFields(), return: true).'</pre>';
+echo '<pre style="font-size: large;">$requestParser->hasPagination()</pre>';
+echo '<pre>'.var_export($requestParser->hasPagination(), return: true).'</pre>';
+echo '<pre style="font-size: large;">$requestParser->hasFilter()</pre>';
+echo '<pre>'.var_export($requestParser->hasFilter(), return: true).'</pre>';
 
 // these methods often return arrays where comma separated query parameter values are processed for ease of use
-var_dump($requestParser->getIncludePaths());
-var_dump($requestParser->getSparseFieldset('user'));
-var_dump($requestParser->getSortFields());
-var_dump($requestParser->getPagination());
-var_dump($requestParser->getFilter());
+echo '<h2>Get query parameters</h2>';
+echo '<pre style="font-size: large;">$requestParser->getIncludePaths()</pre>';
+echo '<pre>'.var_export($requestParser->getIncludePaths(), return: true).'</pre>';
+echo '<pre style="font-size: large;">$requestParser->getSparseFieldset()</pre>';
+echo '<pre>'.var_export($requestParser->getSparseFieldset('user'), return: true).'</pre>';
+echo '<pre style="font-size: large;">$requestParser->getSortFields()</pre>';
+echo '<pre>'.var_export($requestParser->getSortFields(), return: true).'</pre>';
+echo '<pre style="font-size: large;">$requestParser->getPagination()</pre>';
+echo '<pre>'.var_export($requestParser->getPagination(), return: true).'</pre>';
+echo '<pre style="font-size: large;">$requestParser->getFilter()</pre>';
+echo '<pre>'.var_export($requestParser->getFilter(), return: true).'</pre>';
 
 // use for determinging whether keys were given without having to dive deep into the POST data yourself
-var_dump($requestParser->hasAttribute('name'));
-var_dump($requestParser->hasRelationship('ship'));
-var_dump($requestParser->hasMeta('lock'));
+echo '<h2>Check parts of the document</h2>';
+echo '<pre style="font-size: large;">$requestParser->hasAttribute()</pre>';
+echo '<pre>'.var_export($requestParser->hasAttribute('name'), return: true).'</pre>';
+echo '<pre style="font-size: large;">$requestParser->hasRelationship()</pre>';
+echo '<pre>'.var_export($requestParser->hasRelationship('ship'), return: true).'</pre>';
+echo '<pre style="font-size: large;">$requestParser->hasMeta()</pre>';
+echo '<pre>'.var_export($requestParser->hasMeta('lock'), return: true).'</pre>';
 
 // get the raw data from the document, this doesn't (yet) return specific objects
-var_dump($requestParser->getAttribute('name'));
-var_dump($requestParser->getRelationship('ship'));
-var_dump($requestParser->getMeta('lock'));
+echo '<h2>Get parts of the document</h2>';
+echo '<pre style="font-size: large;">$requestParser->getAttribute()</pre>';
+echo '<pre>'.var_export($requestParser->getAttribute('name'), return: true).'</pre>';
+echo '<pre style="font-size: large;">$requestParser->getRelationship()</pre>';
+echo '<pre>'.var_export($requestParser->getRelationship('ship'), return: true).'</pre>';
+echo '<pre style="font-size: large;">$requestParser->getMeta()</pre>';
+echo '<pre>'.var_export($requestParser->getMeta('lock'), return: true).'</pre>';
 
 // get the full document for custom processing
-var_dump($requestParser->getDocument());
+echo '<h2>Get full document</h2>';
+echo '<pre style="font-size: large;">$requestParser->getDocument()</pre>';
+echo '<pre>'.var_export($requestParser->getDocument(), return: true).'</pre>';
diff --git a/examples/resource_human_api.php b/examples/resource_human_api.php
index 64fdc576..6d080737 100644
--- a/examples/resource_human_api.php
+++ b/examples/resource_human_api.php
@@ -10,7 +10,7 @@
 use alsvanzelf\jsonapi\objects\RelationshipsObject;
 use alsvanzelf\jsonapi\objects\ResourceObject;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 $user1  = ExampleDataset::getEntity('user', 1);
 $user42 = ExampleDataset::getEntity('user', 42);
diff --git a/examples/resource_links.php b/examples/resource_links.php
index 6d9e8860..aa4cef1f 100644
--- a/examples/resource_links.php
+++ b/examples/resource_links.php
@@ -5,7 +5,7 @@
 use alsvanzelf\jsonapi\ResourceDocument;
 use alsvanzelf\jsonapi\enums\DocumentLevelEnum;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 $userEntity = ExampleDataset::getEntity('user', 42);
 
diff --git a/examples/resource_nested_relations.php b/examples/resource_nested_relations.php
index b94b07e2..9545d47f 100644
--- a/examples/resource_nested_relations.php
+++ b/examples/resource_nested_relations.php
@@ -5,7 +5,7 @@
 use alsvanzelf\jsonapi\ResourceDocument;
 use alsvanzelf\jsonapi\objects\ResourceObject;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 $userEntity = ExampleDataset::getEntity('user', 42);
 
diff --git a/examples/resource_spec_api.php b/examples/resource_spec_api.php
index fa160d44..e45006df 100644
--- a/examples/resource_spec_api.php
+++ b/examples/resource_spec_api.php
@@ -11,7 +11,7 @@
 use alsvanzelf\jsonapi\objects\RelationshipsObject;
 use alsvanzelf\jsonapi\objects\ResourceObject;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 $user1  = ExampleDataset::getEntity('user', 1);
 $user42 = ExampleDataset::getEntity('user', 42);
diff --git a/examples/status_only.php b/examples/status_only.php
index 94439c01..bcd35226 100644
--- a/examples/status_only.php
+++ b/examples/status_only.php
@@ -4,7 +4,7 @@
 
 use alsvanzelf\jsonapi\MetaDocument;
 
-require 'bootstrap_examples.php';
+require __DIR__.'/bootstrap_examples.php';
 
 /**
  * use jsonapi to send out a status code
diff --git a/phpcs.bonus.xml b/phpcs.bonus.xml
index ee7fe9e0..5cb3deca 100644
--- a/phpcs.bonus.xml
+++ b/phpcs.bonus.xml
@@ -21,5 +21,7 @@
 	<rule ref="Generic.Metrics.CyclomaticComplexity"/>
 	<rule ref="Generic.Metrics.NestingLevel"/>
 	
-	<rule ref="Squiz.Operators.ComparisonOperatorUsage"/>
+	<rule ref="Squiz.Operators.ComparisonOperatorUsage">
+		<exclude name="Squiz.Operators.ComparisonOperatorUsage.ImplicitTrue"/>
+	</rule>
 </ruleset>
diff --git a/phpstan.bonus.neon b/phpstan.bonus.neon
index ae9db4e9..08b9682a 100644
--- a/phpstan.bonus.neon
+++ b/phpstan.bonus.neon
@@ -1,12 +1,5 @@
 includes:
 	- phpstan.neon
-	- vendor/phpstan/phpstan/conf/bleedingEdge.neon
 
 parameters:
-	level: 10
-
-	treatPhpDocTypesAsCertain: true
-
-	# @see https://github.com/phpstan/phpstan-strict-rules
-	strictRules:
-		allRules: true
+	level: max
diff --git a/phpstan.neon b/phpstan.neon
index a5a5f410..67bb4b53 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,20 +1,118 @@
+includes:
+	- vendor/phpstan/phpstan/conf/bleedingEdge.neon
+
 parameters:
 	# slowly increase
-	level: 4
+	level: 9
 	paths:
 		- src/
 		- tests/
 		- examples/
-
+	
 	typeAliases:
-		PHPStanTypeAlias_InternalOptions: 'array<string, bool|int|null|\alsvanzelf\jsonapi\enums\ContentTypeEnum>'
+		PHPStanTypeAlias_Options_CollectionDocument: 'array{includeContainedResources?: bool}'
+		PHPStanTypeAlias_Options_Document: 'array{encodeOptions?: int, prettyPrint?: bool, contentType?: \alsvanzelf\jsonapi\enums\ContentTypeEnum, array?: ?PHPStanTypeAlias_DocumentArray, json?: ?string, jsonpCallback?: ?string}'
+		PHPStanTypeAlias_Options_ErrorsDocument: 'array{includeExceptionTrace?: bool, includeExceptionPrevious?: bool}'
+		PHPStanTypeAlias_Options_ResourceDocument: 'array{includeContainedResources?: bool}'
+		PHPStanTypeAlias_Options_ResourceDocumentAndValidator: 'array{includeContainedResources?: bool, enforceTypeFieldNamespace?: bool}'
+		PHPStanTypeAlias_Options_Validator: 'array{enforceTypeFieldNamespace?: bool}'
+		PHPStanTypeAlias_Options_RequestParser: 'array{useNestedIncludePaths?: bool, useAnnotatedSortFields?: bool}'
+		PHPStanTypeAlias_Options_ErrorObject: 'array{includeExceptionTrace?: bool, stripExceptionBasePath?: ?string}'
+		PHPStanTypeAlias_Options_ErrorsDocumentAndErrorObject: 'array{includeExceptionTrace?: bool, includeExceptionPrevious?: bool, stripExceptionBasePath?: ?string}'
+		
+		PHPStanTypeAlias_DefaultOptions_CollectionDocument: 'array{includeContainedResources: bool}'
+		PHPStanTypeAlias_DefaultOptions_Document: 'array{encodeOptions: int, prettyPrint: bool, contentType: \alsvanzelf\jsonapi\enums\ContentTypeEnum, array: ?PHPStanTypeAlias_DocumentArray, json: ?string, jsonpCallback: ?string}'
+		PHPStanTypeAlias_DefaultOptions_ErrorsDocument: 'array{includeExceptionTrace: bool, includeExceptionPrevious: bool}'
+		PHPStanTypeAlias_DefaultOptions_ResourceDocument: 'array{includeContainedResources: bool}'
+		PHPStanTypeAlias_DefaultOptions_ResourceDocumentAndValidator: 'array{includeContainedResources: bool, enforceTypeFieldNamespace: bool}'
+		PHPStanTypeAlias_DefaultOptions_Validator: 'array{enforceTypeFieldNamespace: bool}'
+		PHPStanTypeAlias_DefaultOptions_RequestParser: 'array{useNestedIncludePaths: bool, useAnnotatedSortFields: bool}'
+		PHPStanTypeAlias_DefaultOptions_ErrorObject: 'array{includeExceptionTrace: bool, stripExceptionBasePath: ?string}'
+		PHPStanTypeAlias_DefaultOptions_ErrorsDocumentAndErrorObject: 'array{includeExceptionTrace: bool, includeExceptionPrevious: bool, stripExceptionBasePath: ?string}'
+		
+		PHPStanTypeAlias_DocumentArray: 'array<string, mixed>'
+		PHPStanTypeAlias_QueryParameters: 'array{fields?: array<array-key, string>, filter?: string|array<array-key, string>, include?: string, page?: array<array-key, string>, sort?: string}'
 	
-	treatPhpDocTypesAsCertain: false
+	treatPhpDocTypesAsCertain: true
 	
 	strictRules:
-		allRules: false
+		allRules: true
 	
 	reportUnmatchedIgnoredErrors: true
 	ignoreErrors:
 		# add cases to ignore because they are too much work for now
 		# @see https://phpstan.org/user-guide/ignoring-errors#ignoring-in-configuration-file
+		
+		# testing AtMemberManager trait
+		-
+			messages:
+				- '#Call to an undefined method object::hasAtMembers\(\)#'
+				- '#Call to an undefined method object::getAtMembers\(\)#'
+				- '#Call to an undefined method object::addAtMember\(\)#'
+			identifier: method.notFound
+			path: tests/helpers/AtMemberManagerTest.php
+		
+		# testing ExtensionMemberManager trait
+		-
+			messages:
+				- '#Call to an undefined method object::addExtensionMember\(\)#'
+				- '#Call to an undefined method object::hasExtensionMembers\(\)#'
+				- '#Call to an undefined method object::getExtensionMembers\(\)#'
+			identifier: method.notFound
+			path: tests/helpers/ExtensionMemberManagerTest.php
+		
+		# testing HttpStatusCodeManager trait
+		-
+			messages:
+				- '#Call to an undefined method object::setHttpStatusCode\(\)#'
+				- '#Call to an undefined method object::hasHttpStatusCode\(\)#'
+				- '#Call to an undefined method object::getHttpStatusCode\(\)#'
+			identifier: method.notFound
+			path: tests/helpers/HttpStatusCodeManagerTest.php
+		
+		# testing LinksManager trait
+		-
+			messages:
+				- '#Call to an undefined method object::addLink\(\)#'
+				- '#Call to an undefined method object::addLinkObject\(\)#'
+				- '#Call to an undefined method object::setLinksObject\(\)#'
+				- '#Call to an undefined method object::toArray\(\)#'
+			identifier: method.notFound
+			path: tests/helpers/LinksManagerTest.php
+
+		# mixed is only used for input from library implementations
+		-
+			identifier: argument.type
+			message: '#Parameter \#\d \$.+ of function .+ expects .+, mixed given#'
+			path: src/helpers/RequestParser.php
+
+		# mixed is only used for input from library implementations
+		-
+			identifier: argument.type
+			message: '#Parameter \#\d \$.+ of class .+ constructor expects .+, mixed given#'
+			paths:
+				- src/helpers/RequestParser.php
+				- src/objects/ResourceObject.php
+
+		# mixed is only used for input from library implementations
+		-
+			identifier: argument.type
+			message: '#Parameter \#\d \$.+ of static method .+ expects .+, mixed given#'
+			path: tests/*
+
+		# mixed is only used for input from library implementations
+		-
+			identifier: offsetAccess.nonOffsetAccessible
+			message: '#Cannot access offset .+ on mixed#'
+			paths:
+				- src/helpers/RequestParser.php
+				- tests/*
+
+		# allow internal methods in examples and tests
+		-
+			identifiers:
+				- method.internal
+				- staticMethod.internalClass
+			paths:
+				- examples/*
+				- tests/*
diff --git a/rector.php b/rector.php
index bba93d87..4d2b6b90 100644
--- a/rector.php
+++ b/rector.php
@@ -2,9 +2,18 @@
 
 declare(strict_types=1);
 
+use Rector\CodeQuality\Rector\FuncCall\SortNamedParamRector;
+use Rector\CodeQuality\Rector\FunctionLike\SimplifyUselessVariableRector;
+use Rector\CodeQuality\Rector\Identical\FlipTypeControlToUseExclusiveTypeRector;
+use Rector\CodeQuality\Rector\If_\SimplifyIfReturnBoolRector;
+use Rector\CodingStyle\Rector\ClassLike\NewlineBetweenClassLikeStmtsRector;
+use Rector\CodingStyle\Rector\ClassMethod\NewlineBeforeNewAssignSetRector;
+use Rector\CodingStyle\Rector\Stmt\NewlineAfterStatementRector;
+use Rector\CodingStyle\Rector\String_\SimplifyQuoteEscapeRector;
 use Rector\Config\RectorConfig;
+use Rector\DeadCode\Rector\Property\RemoveUnusedPrivatePropertyRector;
 use Rector\Php70\Rector\StmtsAwareInterface\IfIssetToCoalescingRector;
-use Rector\TypeDeclaration\Rector\Class_\AddTestsVoidReturnTypeWhereNoReturnRector;
+use Rector\TypeDeclarationDocblocks\Rector\ClassMethod\DocblockGetterReturnArrayFromPropertyDocblockVarRector;
 use Rector\TypeDeclaration\Rector\StmtsAwareInterface\DeclareStrictTypesRector;
 
 // @see https://github.com/rectorphp/rector/blob/main/docs/rector_rules_overview.md for more rules
@@ -15,24 +24,67 @@
 		__DIR__ . '/tests',
 		__DIR__ . '/examples',
 	])
+	->withRootFiles()
 	->withRules([
 		DeclareStrictTypesRector::class,
-		AddTestsVoidReturnTypeWhereNoReturnRector::class,
 	])
 	->withSkip([
 		// better explicit readability
+		FlipTypeControlToUseExclusiveTypeRector::class,
 		IfIssetToCoalescingRector::class,
+		SimplifyUselessVariableRector::class,
+		SimplifyIfReturnBoolRector::class,
+		
+		// not all rules from code style
+		NewlineAfterStatementRector::class,
+		NewlineBeforeNewAssignSetRector::class,
+		NewlineBetweenClassLikeStmtsRector::class,
+		SimplifyQuoteEscapeRector::class,
+		
+		// rely on types from interfaces
+		DocblockGetterReturnArrayFromPropertyDocblockVarRector::class,
+		
+		// better readability using function declaration sorting
+		SortNamedParamRector::class,
+		
+		// explicit testing private properties
+		RemoveUnusedPrivatePropertyRector::class => [
+			'tests/ConverterTest.php',
+		],
 	])
 	
 	// tab-based indenting
 	->withIndent(indentChar: "\t", indentSize: 1)
+	// importing FQNs
+	->withImportNames(importShortClasses: false)
 	
 	// lowest supported php version
 	->withPhpSets(php82: true)
 	
-	// slowly increase levels
-	->withTypeCoverageLevel(1)
-	->withDeadCodeLevel(1)
+	// expand with new keys
+	->withPreparedSets(
+		deadCode: true,
+		codeQuality: true,
+		codingStyle: true,
+		typeDeclarations: true,
+		typeDeclarationDocblocks: true,
+		privatization: true,
+		phpunitCodeQuality: true,
+		
+		// prefer own style
+		// naming: true,
+		// instanceOf: true,
+		// earlyReturn: true,
+		// rectorPreset: true,
+		
+		// not used
+		// carbon: true,
+		// doctrineCodeQuality: true,
+		// symfonyCodeQuality: true,
+		// symfonyConfigs: true,
+	)
 	
-	// @todo add `->withPreparedSets()` once on a higher level with other rules
+	// vendor sets
+	->withAttributesSets()
+	->withComposerBased(phpunit: true)
 ;
diff --git a/script/lint b/script/lint
index 41580fcc..e9a265f8 100755
--- a/script/lint
+++ b/script/lint
@@ -5,7 +5,7 @@ SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"
 cd $SCRIPT_DIR/..
 
 # whether to run bonus levels by default, or only when requested
-BONUS_DEFAULT=0
+BONUS_DEFAULT=1
 
 # docker configured and not inside docker
 CONSOLE_PREFIX=""
diff --git a/src/CollectionDocument.php b/src/CollectionDocument.php
index d3663039..9bbed6e2 100644
--- a/src/CollectionDocument.php
+++ b/src/CollectionDocument.php
@@ -21,8 +21,8 @@
 class CollectionDocument extends DataDocument implements PaginableInterface, ResourceContainerInterface {
 	/** @var ResourceInterface[] */
 	protected array $resources = [];
-	/** @var PHPStanTypeAlias_InternalOptions */
-	protected static array $defaults = [
+	/** @var PHPStanTypeAlias_DefaultOptions_CollectionDocument */
+	protected static array $collectionDocumentDefaults = [
 		/**
 		 * add resources inside relationships to /included when adding resources to the collection
 		 */
@@ -89,7 +89,7 @@ public function setPaginationLinks(
 	 * 
 	 * adds included resources if found inside the resource's relationships, unless $options['includeContainedResources'] is set to false
 	 * 
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see CollectionDocument::$defaults}
+	 * @param PHPStanTypeAlias_Options_CollectionDocument $options {@see CollectionDocument::$collectionDocumentDefaults}
 	 * 
 	 * @throws InputException if the resource is empty
 	 */
@@ -98,7 +98,7 @@ public function addResource(ResourceInterface $resource, array $options=[]): voi
 			throw new InputException('does not make sense to add empty resources to a collection');
 		}
 		
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$collectionDocumentDefaults, ...$options];
 		
 		$this->validator->claimUsedResourceIdentifier($resource);
 		
diff --git a/src/Document.php b/src/Document.php
index 0c2dfcdd..3af54d97 100644
--- a/src/Document.php
+++ b/src/Document.php
@@ -47,8 +47,8 @@ abstract class Document implements DocumentInterface, \JsonSerializable, HasLink
 	protected array $extensions = [];
 	/** @var ProfileInterface[] */
 	protected array $profiles = [];
-	/** @var PHPStanTypeAlias_InternalOptions */
-	protected static array $defaults = [
+	/** @var PHPStanTypeAlias_DefaultOptions_Document */
+	protected static array $documentDefaults = [
 		/**
 		 * encode to json with these default options
 		 */
@@ -140,7 +140,6 @@ public function setDescribedByLink(string $href, array $meta=[]): void {
 	}
 	
 	/**
-	 * @throws InputException if the $level is unknown
 	 * @throws InputException if the $level is DocumentLevelEnum::Resource
 	 */
 	public function addMeta(string $key, mixed $value, DocumentLevelEnum $level=DocumentLevelEnum::Root): void {
@@ -163,9 +162,6 @@ public function addMeta(string $key, mixed $value, DocumentLevelEnum $level=Docu
 			
 			case DocumentLevelEnum::Resource:
 				throw new InputException('level "resource" can only be set on a ResourceDocument');
-			
-			default:
-				throw new InputException('unknown level "'.$level->value.'"');
 		}
 	}
 	
@@ -177,6 +173,7 @@ public function setMetaObject(MetaObject $metaObject): void {
 		$this->meta = $metaObject;
 	}
 	
+	/** @phpstan-assert JsonapiObject $this->jsonapi */
 	public function setJsonapiObject(JsonapiObject $jsonapiObject): void {
 		$this->jsonapi = $jsonapiObject;
 	}
@@ -261,10 +258,11 @@ public function toArray(): array {
 	}
 	
 	/**
-	 * @throws \JsonException
+	 * @throws \JsonException if encoding fails
+	 * @throws Exception if encoding fails and $options['encodeOptions'] doesn't include JSON_THROW_ON_ERROR
 	 */
 	public function toJson(array $options=[]): string {
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$documentDefaults, ...$options];
 		
 		$array = $options['array'] ?? $this->toArray();
 		
@@ -274,6 +272,11 @@ public function toJson(array $options=[]): string {
 		
 		$json = json_encode($array, $options['encodeOptions']);
 		
+		// we can't use exceptions because $options['encodeOptions'] might be overridden to silence them
+		if ($json === false) {
+			throw new Exception('failed to encode json: '.json_last_error_msg());
+		}
+		
 		if ($options['jsonpCallback'] !== null) {
 			$json = $options['jsonpCallback'].'('.$json.')';
 		}
@@ -282,7 +285,7 @@ public function toJson(array $options=[]): string {
 	}
 	
 	public function sendResponse(array $options=[]): void {
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$documentDefaults, ...$options];
 		
 		if ($this->httpStatusCode === 204) {
 			http_response_code($this->httpStatusCode);
@@ -303,6 +306,9 @@ public function sendResponse(array $options=[]): void {
 	 * JsonSerializable
 	 */
 	
+	/**
+	 * @return array<string, mixed>
+	 */
 	#[\ReturnTypeWillChange]
 	public function jsonSerialize(): array {
 		return $this->toArray();
diff --git a/src/ErrorsDocument.php b/src/ErrorsDocument.php
index 546fbab1..ca15c6a5 100644
--- a/src/ErrorsDocument.php
+++ b/src/ErrorsDocument.php
@@ -13,10 +13,10 @@
 class ErrorsDocument extends Document {
 	/** @var ErrorObject[] */
 	protected array $errors = [];
-	/** @var array<number, array<number, true>> */
-	protected array $httpStatusCodes;
-	/** @var PHPStanTypeAlias_InternalOptions */
-	protected static array $defaults = [
+	/** @var array<string, array<int, true>> */
+	protected array $httpStatusCodes = [];
+	/** @var PHPStanTypeAlias_DefaultOptions_ErrorsDocument */
+	protected static array $errorsDocumentDefaults = [
 		/**
 		 * add the trace of exceptions when adding exceptions
 		 * in some cases it might be handy to disable if traces are too big
@@ -42,10 +42,10 @@ public function __construct(?ErrorObject $errorObject=null) {
 	 */
 	
 	/**
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ErrorsDocument::$defaults}
+	 * @param PHPStanTypeAlias_Options_ErrorsDocument $options {@see ErrorsDocument::$errorsDocumentDefaults}
 	 */
 	public static function fromException(\Throwable $exception, array $options=[]): static {
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$errorsDocumentDefaults, ...$options];
 		
 		$errorsDocument = new static();
 		$errorsDocument->addException($exception, $options);
@@ -58,10 +58,10 @@ public static function fromException(\Throwable $exception, array $options=[]):
 	 * 
 	 * recursively adds multiple ErrorObjects if $exception carries a ->getPrevious()
 	 * 
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ErrorsDocument::$defaults}
+	 * @param PHPStanTypeAlias_Options_ErrorsDocumentAndErrorObject $options {@see ErrorsDocument::$errorsDocumentDefaults}
 	 */
 	public function addException(\Throwable $exception, array $options=[]): void {
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$errorsDocumentDefaults, ...$options];
 		
 		$this->addErrorObject(ErrorObject::fromException($exception, $options));
 		
@@ -137,27 +137,28 @@ public function toArray(): array {
 	protected function determineHttpStatusCode(string|int $httpStatusCode): int {
 		// add the new code
 		$category = substr((string) $httpStatusCode, 0, 1);
-		$this->httpStatusCodes[$category][$httpStatusCode] = true;
+		$category .= 'xx'; // help phpstan understand the array-key is a string not an int
+		$this->httpStatusCodes[$category][(int) $httpStatusCode] = true;
 		
-		$advisedStatusCode = $httpStatusCode;
+		$advisedStatusCode = (int) $httpStatusCode;
 		
 		// when there's multiple, give preference to 5xx errors
-		if (isset($this->httpStatusCodes['5']) && isset($this->httpStatusCodes['4'])) {
+		if (isset($this->httpStatusCodes['5xx']) && isset($this->httpStatusCodes['4xx'])) {
 			// use a generic one
 			$advisedStatusCode = 500;
 		}
-		elseif (isset($this->httpStatusCodes['5'])) {
-			if (count($this->httpStatusCodes['5']) === 1) {
-				$advisedStatusCode = key($this->httpStatusCodes['5']);
+		elseif (isset($this->httpStatusCodes['5xx'])) {
+			if (count($this->httpStatusCodes['5xx']) === 1) {
+				$advisedStatusCode = key($this->httpStatusCodes['5xx']);
 			}
 			else {
 				// use a generic one
 				$advisedStatusCode = 500;
 			}
 		}
-		elseif (isset($this->httpStatusCodes['4'])) {
-			if (count($this->httpStatusCodes['4']) === 1) {
-				$advisedStatusCode = key($this->httpStatusCodes['4']);
+		elseif (isset($this->httpStatusCodes['4xx'])) {
+			if (count($this->httpStatusCodes['4xx']) === 1) {
+				$advisedStatusCode = key($this->httpStatusCodes['4xx']);
 			}
 			else {
 				// use a generic one
@@ -165,6 +166,6 @@ protected function determineHttpStatusCode(string|int $httpStatusCode): int {
 			}
 		}
 		
-		return (int) $advisedStatusCode;
+		return $advisedStatusCode;
 	}
 }
diff --git a/src/MetaDocument.php b/src/MetaDocument.php
index 585daf95..40d0a599 100644
--- a/src/MetaDocument.php
+++ b/src/MetaDocument.php
@@ -28,9 +28,6 @@ public static function fromArray(array $meta): static {
 		return $metaDocument;
 	}
 	
-	/**
-	 * @param object $meta
-	 */
 	public static function fromObject(object $meta): static {
 		$array = Converter::objectToArray($meta);
 		
diff --git a/src/ResourceDocument.php b/src/ResourceDocument.php
index 17bfda7d..6b9f4b39 100644
--- a/src/ResourceDocument.php
+++ b/src/ResourceDocument.php
@@ -27,8 +27,8 @@
  */
 class ResourceDocument extends DataDocument implements HasAttributesInterface, ResourceInterface {
 	protected ResourceIdentifierObject|ResourceObject $resource;
-	/** @var PHPStanTypeAlias_InternalOptions */
-	protected static array $defaults = [
+	/** @var PHPStanTypeAlias_DefaultOptions_ResourceDocument */
+	protected static array $resourceDocumentDefaults = [
 		/**
 		 * add resources inside relationships to /included when adding resources to the collection
 		 */
@@ -51,7 +51,8 @@ public function __construct(?string $type=null, string|int|null $id=null) {
 	 */
 	
 	/**
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ResourceDocument::$defaults} {@see ResourceObject::$defaults}
+	 * @param array<string, mixed> $attributes
+	 * @param PHPStanTypeAlias_Options_ResourceDocumentAndValidator $options {@see ResourceDocument::$resourceDocumentDefaults} {@see ResourceObject::$resourceObjectDefaults}
 	 */
 	public static function fromArray(
 		array $attributes,
@@ -66,7 +67,7 @@ public static function fromArray(
 	}
 	
 	/**
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ResourceDocument::$defaults}
+	 * @param PHPStanTypeAlias_Options_ResourceDocumentAndValidator $options {@see ResourceDocument::$resourceDocumentDefaults}
 	 */
 	public static function fromObject(
 		object $attributes,
@@ -82,8 +83,8 @@ public static function fromObject(
 	/**
 	 * add key-value pairs to the resource's attributes
 	 * 
-	 * @param mixed                            $value   objects will be converted using `get_object_vars()`
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ResourceDocument::$defaults}
+	 * @param mixed                             $value   objects will be converted using `get_object_vars()`
+	 * @param PHPStanTypeAlias_Options_Validator $options {@see ResourceDocument::$resourceDocumentDefaults}
 	 */
 	public function add(string $key, mixed $value, array $options=[]): void {
 		if ($this->resource instanceof ResourceObject === false) {
@@ -101,7 +102,7 @@ public function add(string $key, mixed $value, array $options=[]): void {
 	 * @param CollectionDocument|ResourceInterface|ResourceInterface[]|null $relation 
 	 * @param array<string, ?string>                                        $links
 	 * @param array<string, mixed>                                          $meta
-	 * @param PHPStanTypeAlias_InternalOptions                              $options {@see ResourceDocument::$defaults}
+	 * @param PHPStanTypeAlias_Options_ResourceDocument                     $options {@see ResourceDocument::$resourceDocumentDefaults}
 	 */
 	public function addRelationship(
 		string $key,
@@ -114,7 +115,7 @@ public function addRelationship(
 			throw new Exception('the resource is an identifier-only object');
 		}
 		
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$resourceDocumentDefaults, ...$options];
 		
 		$relationshipObject = $this->resource->addRelationship($key, $relation, $links, $meta);
 		
@@ -188,7 +189,7 @@ public function setLocalId(string|int $localId): void {
 	}
 	
 	/**
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ResourceObject::$defaults}
+	 * @param PHPStanTypeAlias_Options_Validator $options {@see ResourceObject::$resourceObjectDefaults}
 	 */
 	public function setAttributesObject(AttributesObject $attributesObject, array $options=[]): void {
 		if ($this->resource instanceof ResourceObject === false) {
@@ -203,14 +204,14 @@ public function setAttributesObject(AttributesObject $attributesObject, array $o
 	 * 
 	 * adds included resources if found inside the RelationshipObject, unless $options['includeContainedResources'] is set to false
 	 * 
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ResourceDocument::$defaults}
+	 * @param PHPStanTypeAlias_Options_ResourceDocument $options {@see ResourceDocument::$resourceDocumentDefaults}
 	 */
 	public function addRelationshipObject(string $key, RelationshipObject $relationshipObject, array $options=[]): void {
 		if ($this->resource instanceof ResourceObject === false) {
 			throw new Exception('the resource is an identifier-only object');
 		}
 		
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$resourceDocumentDefaults, ...$options];
 		
 		$this->resource->addRelationshipObject($key, $relationshipObject);
 		
@@ -224,14 +225,14 @@ public function addRelationshipObject(string $key, RelationshipObject $relations
 	 * 
 	 * adds included resources if found inside the RelationshipObjects inside the RelationshipsObject, unless $options['includeContainedResources'] is set to false
 	 * 
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ResourceDocument::$defaults}
+	 * @param PHPStanTypeAlias_Options_ResourceDocument $options {@see ResourceDocument::$resourceDocumentDefaults}
 	 */
 	public function setRelationshipsObject(RelationshipsObject $relationshipsObject, array $options=[]): void {
 		if ($this->resource instanceof ResourceObject === false) {
 			throw new Exception('the resource is an identifier-only object');
 		}
 		
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$resourceDocumentDefaults, ...$options];
 		
 		$this->resource->setRelationshipsObject($relationshipsObject);
 		
@@ -249,7 +250,7 @@ public function setRelationshipsObject(RelationshipsObject $relationshipsObject,
 	 * 
 	 * adds included resources if found inside the resource's relationships, unless $options['includeContainedResources'] is set to false
 	 * 
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ResourceDocument::$defaults}
+	 * @param PHPStanTypeAlias_Options_ResourceDocument $options {@see ResourceDocument::$resourceDocumentDefaults}
 	 * 
 	 * @throws InputException if the $resource is a ResourceDocument itself
 	 */
@@ -260,7 +261,7 @@ public function setPrimaryResource(ResourceInterface $resource, array $options=[
 		
 		/** @var ResourceIdentifierObject|ResourceObject $resource */
 		
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$resourceDocumentDefaults, ...$options];
 		
 		$this->resource = $resource;
 		
@@ -293,7 +294,7 @@ public function toArray(): array {
 	 */
 	
 	public function addAttribute(string $key, mixed $value, array $options=[]): void {
-		$this->add($key, $value);
+		$this->add($key, $value, $options);
 	}
 	
 	/**
diff --git a/src/exceptions/DuplicateException.php b/src/exceptions/DuplicateException.php
index a1c5c9a1..a1a7c176 100644
--- a/src/exceptions/DuplicateException.php
+++ b/src/exceptions/DuplicateException.php
@@ -7,7 +7,7 @@
 use alsvanzelf\jsonapi\exceptions\Exception;
 
 class DuplicateException extends Exception {
-	public function __construct($message='', $code=409, $previous=null) {
+	public function __construct(string $message='', int $code=409, ?\Throwable $previous=null) {
 		parent::__construct($message, $code, $previous);
 	}
 }
diff --git a/src/exceptions/InputException.php b/src/exceptions/InputException.php
index ce121c14..4f049cb3 100644
--- a/src/exceptions/InputException.php
+++ b/src/exceptions/InputException.php
@@ -7,7 +7,7 @@
 use alsvanzelf\jsonapi\exceptions\Exception;
 
 class InputException extends Exception {
-	public function __construct($message='', $code=400, $previous=null) {
+	public function __construct(string $message='', int $code=400, ?\Throwable $previous=null) {
 		parent::__construct($message, $code, $previous);
 	}
 }
diff --git a/src/helpers/Converter.php b/src/helpers/Converter.php
index b0c0edd3..5851a686 100644
--- a/src/helpers/Converter.php
+++ b/src/helpers/Converter.php
@@ -5,6 +5,7 @@
 namespace alsvanzelf\jsonapi\helpers;
 
 use alsvanzelf\jsonapi\enums\ContentTypeEnum;
+use alsvanzelf\jsonapi\exceptions\Exception;
 use alsvanzelf\jsonapi\interfaces\ExtensionInterface;
 use alsvanzelf\jsonapi\interfaces\ObjectInterface;
 use alsvanzelf\jsonapi\interfaces\ProfileInterface;
@@ -13,6 +14,9 @@
  * @internal
  */
 class Converter {
+	/**
+	 * @return array<string, mixed>
+	 */
 	public static function objectToArray(object $object): array {
 		if ($object instanceof ObjectInterface) {
 			return $object->toArray();
@@ -23,10 +27,16 @@ public static function objectToArray(object $object): array {
 	
 	/**
 	 * @see https://stackoverflow.com/questions/7593969/regex-to-split-camelcase-or-titlecase-advanced/7599674#7599674
+	 * 
+	 * @throws Exception if string is impossible to split to words
 	 */
 	public static function camelCaseToWords(string $camelCase): string {
 		$parts = preg_split('/(?<=[a-z])(?=[A-Z])|(?<=[A-Z])(?=[A-Z][a-z])/', $camelCase);
 		
+		if ($parts === false) {
+			throw new Exception('failed to convert camel case string to words');
+		}
+		
 		return implode(' ', $parts);
 	}
 	
diff --git a/src/helpers/RequestParser.php b/src/helpers/RequestParser.php
index 0863c306..5c2ac6ad 100644
--- a/src/helpers/RequestParser.php
+++ b/src/helpers/RequestParser.php
@@ -15,8 +15,8 @@
  * that might break the class since we use `new static()`
  */
 class RequestParser {
-	/** @var PHPStanTypeAlias_InternalOptions */
-	protected static array $defaults = [
+	/** @var PHPStanTypeAlias_DefaultOptions_RequestParser */
+	protected static array $requestParserDefaults = [
 		/**
 		 * reformat the include query parameter paths to nested arrays
 		 * this allows easier processing on each step of the chain
@@ -31,9 +31,9 @@ class RequestParser {
 	];
 	
 	/**
-	 * @param string                                         $selfLink        the uri used to make this request {@see getSelfLink()}
-	 * @param array<string, string|array<array-key, string>> $queryParameters all query parameters defined by the specification
-	 * @param array<string, mixed>                           $document        the request jsonapi document
+	 * @param string                           $selfLink        the uri used to make this request {@see getSelfLink()}
+	 * @param PHPStanTypeAlias_QueryParameters $queryParameters all query parameters defined by the specification
+	 * @param array<string, mixed>             $document        the request jsonapi document
 	 * 
 	 * @throws \JsonException if $document's content type is json but it can't be json decoded
 	 */
@@ -44,20 +44,30 @@ public function __construct(
 	) {}
 	
 	public static function fromSuperglobals(): static {
+		/**
+		 * @var array{
+		 *      REQUEST_SCHEME?: string,
+		 *      HTTP_HOST?: string,
+		 *      REQUEST_URI?: string,
+		 *      CONTENT_TYPE?: string
+		 * } $_SERVER
+		 */
+		
 		$selfLink = '';
 		if (isset($_SERVER['REQUEST_SCHEME']) && isset($_SERVER['HTTP_HOST']) && isset($_SERVER['REQUEST_URI'])) {
 			$selfLink = $_SERVER['REQUEST_SCHEME'].'://'.$_SERVER['HTTP_HOST'].$_SERVER['REQUEST_URI'];
 		}
 		
+		/** @var PHPStanTypeAlias_QueryParameters $queryParameters */
 		$queryParameters = $_GET;
 		
 		$document = $_POST;
 		if ($document === [] && isset($_SERVER['CONTENT_TYPE'])) {
-			$documentIsJsonapi = (str_contains((string) $_SERVER['CONTENT_TYPE'], ContentTypeEnum::Official->value));
-			$documentIsJson    = (str_contains((string) $_SERVER['CONTENT_TYPE'], ContentTypeEnum::Debug->value));
+			$documentIsJsonapi = (str_contains($_SERVER['CONTENT_TYPE'], ContentTypeEnum::Official->value));
+			$documentIsJson    = (str_contains($_SERVER['CONTENT_TYPE'], ContentTypeEnum::Debug->value));
 			
 			$document = file_get_contents('php://input');
-			if ($document === '') {
+			if ($document === '' || $document === false) {
 				$document = [];
 			}
 			elseif ($documentIsJsonapi || $documentIsJson) {
@@ -82,6 +92,8 @@ public static function fromPsrRequest(ServerRequestInterface|RequestInterface $r
 			parse_str($request->getUri()->getQuery(), $queryParameters);
 		}
 		
+		/** @var PHPStanTypeAlias_QueryParameters $queryParameters */
+		
 		if ($request->getBody()->getContents() === '') {
 			$document = [];
 		}
@@ -102,7 +114,7 @@ public function getSelfLink(): string {
 	}
 	
 	public function hasIncludePaths(): bool {
-		return isset($this->queryParameters['include']);
+		return $this->hasQueryParameter('include');
 	}
 	
 	/**
@@ -111,17 +123,17 @@ public function hasIncludePaths(): bool {
 	 * the nested format allows easier processing on each step of the chain
 	 * the raw format allows for custom processing
 	 * 
-	 * @param  PHPStanTypeAlias_InternalOptions $options {@see RequestParser::$defaults}
-	 * @return string[]|array
+	 * @param  PHPStanTypeAlias_Options_RequestParser $options {@see RequestParser::$requestParserDefaults}
+	 * @return array<string>|array<array-key, mixed>
 	 */
 	public function getIncludePaths(array $options=[]): array {
-		if ($this->queryParameters['include'] === '') {
+		if ($this->getQueryParameter('include') === '') {
 			return [];
 		}
 		
-		$includePaths = explode(',', (string) $this->queryParameters['include']);
+		$includePaths = explode(',', $this->getQueryParameter('include'));
 		
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$requestParserDefaults, ...$options];
 		if ($options['useNestedIncludePaths'] === false) {
 			return $includePaths;
 		}
@@ -143,22 +155,22 @@ public function getIncludePaths(array $options=[]): array {
 	}
 	
 	public function hasSparseFieldset(string $type): bool {
-		return isset($this->queryParameters['fields'][$type]);
+		return isset($this->getQueryParameter('fields')[$type]);
 	}
 	
 	/**
 	 * @return string[]
 	 */
 	public function getSparseFieldset(string $type): array {
-		if ($this->queryParameters['fields'][$type] === '') {
+		if ($this->getQueryParameter('fields')[$type] === '') {
 			return [];
 		}
 		
-		return explode(',', (string) $this->queryParameters['fields'][$type]);
+		return explode(',', $this->getQueryParameter('fields')[$type]);
 	}
 	
 	public function hasSortFields(): bool {
-		return isset($this->queryParameters['sort']);
+		return $this->hasQueryParameter('sort');
 	}
 	
 	/**
@@ -169,20 +181,20 @@ public function hasSortFields(): bool {
 	 * 
 	 * @todo return some kind of SortFieldObject
 	 * 
-	 * @param  PHPStanTypeAlias_InternalOptions $options {@see RequestParser::$defaults}
+	 * @param  PHPStanTypeAlias_Options_RequestParser $options {@see RequestParser::$requestParserDefaults}
 	 * @return string[]|array<array{
 	 *         field: string, // the sort field, without any minus sign for descending sort order
 	 *         order: SortOrderEnum,
 	 * }>
 	 */
 	public function getSortFields(array $options=[]): array {
-		if ($this->queryParameters['sort'] === '') {
+		if ($this->getQueryParameter('sort') === '') {
 			return [];
 		}
 		
-		$fields = explode(',', (string) $this->queryParameters['sort']);
+		$fields = explode(',', $this->getQueryParameter('sort'));
 		
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$requestParserDefaults, ...$options];
 		if ($options['useAnnotatedSortFields'] === false) {
 			return $fields;
 		}
@@ -206,7 +218,7 @@ public function getSortFields(array $options=[]): array {
 	}
 	
 	public function hasPagination(): bool {
-		return isset($this->queryParameters['page']);
+		return $this->hasQueryParameter('page');
 	}
 	
 	/**
@@ -216,18 +228,18 @@ public function hasPagination(): bool {
 	 * @return array<string, string>
 	 */
 	public function getPagination(): array {
-		return $this->queryParameters['page'];
+		return $this->getQueryParameter('page');
 	}
 	
 	public function hasFilter(): bool {
-		return isset($this->queryParameters['filter']);
+		return $this->hasQueryParameter('filter');
 	}
 	
 	/**
 	 * @return string|array<array-key, string>
 	 */
 	public function getFilter(): string|array {
-		return $this->queryParameters['filter'];
+		return $this->getQueryParameter('filter');
 	}
 	
 	public function hasLocalId(): bool {
@@ -235,7 +247,7 @@ public function hasLocalId(): bool {
 	}
 	
 	public function getLocalId(): string {
-		return $this->document['data']['lid'];
+		return $this->document['data']['lid']; // @phpstan-ignore return.type (implementation returns mixed)
 	}
 	
 	public function hasAttribute(string $attributeName): bool {
@@ -270,7 +282,7 @@ public function hasRelationship(string $relationshipName): bool {
 	 * @return ?array<string, mixed>
 	 */
 	public function getRelationship(string $relationshipName): ?array {
-		return $this->document['data']['relationships'][$relationshipName];
+		return $this->document['data']['relationships'][$relationshipName]; // @phpstan-ignore return.type (implementation returns mixed)
 	}
 	
 	public function hasMeta(string $metaKey): bool {
@@ -294,4 +306,28 @@ public function getMeta(string $metaKey): mixed {
 	public function getDocument(): array {
 		return $this->document;
 	}
+	
+	/**
+	 * @internal
+	 */
+	protected function hasQueryParameter(string $key): bool {
+		return isset($this->queryParameters[$key]);
+	}
+	
+	/**
+	 * @internal
+	 * 
+	 * @return ($key is 'fields'|'page' ? array<array-key, string> : string)
+	 */
+	protected function getQueryParameter(string $key): string|array {
+		return match ($key) {
+			// array shape
+			'fields', 'page'  => $this->queryParameters[$key] ?? [],
+			// string shape
+			'include', 'sort' => $this->queryParameters[$key] ?? '',
+			// mixed shape
+			'filter'          => $this->queryParameters[$key] ?? '',
+			default           => $this->queryParameters[$key] ?? '',
+		};
+	}
 }
diff --git a/src/helpers/Validator.php b/src/helpers/Validator.php
index d1010b61..981168c3 100644
--- a/src/helpers/Validator.php
+++ b/src/helpers/Validator.php
@@ -17,8 +17,8 @@ class Validator {
 	protected array $usedFields = [];
 	/** @var array<string, true> */
 	protected array $usedResourceIdentifiers = [];
-	/** @var PHPStanTypeAlias_InternalOptions */
-	protected static array $defaults = [
+	/** @var PHPStanTypeAlias_DefaultOptions_Validator */
+	protected static array $validatorDefaults = [
 		/**
 		 * blocks 'type' as a keyword inside attributes or relationships
 		 * the specification doesn't allow this as 'type' is already set at the root of a resource
@@ -33,12 +33,12 @@ class Validator {
 	 * @see https://jsonapi.org/format/1.1/#document-resource-object-fields
 	 * 
 	 * @param  string[]                         $fieldNames
-	 * @param  PHPStanTypeAlias_InternalOptions $options    {@see Validator::$defaults}
+	 * @param  PHPStanTypeAlias_Options_Validator $options    {@see Validator::$validatorDefaults}
 	 * 
 	 * @throws DuplicateException
 	 */
 	public function claimUsedFields(array $fieldNames, ObjectContainerEnum $objectContainer, array $options=[]): void {
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$validatorDefaults, ...$options];
 		
 		foreach ($fieldNames as $fieldName) {
 			if (isset($this->usedFields[$fieldName]) === false) {
diff --git a/src/interfaces/DocumentInterface.php b/src/interfaces/DocumentInterface.php
index fc80a4a0..5463efc7 100644
--- a/src/interfaces/DocumentInterface.php
+++ b/src/interfaces/DocumentInterface.php
@@ -17,7 +17,7 @@ public function toArray(): array;
 	/**
 	 * generate json with the contents of the document, used by {@see ->sendResponse()}
 	 * 
-	 * @param PHPStanTypeAlias_InternalOptions $options
+	 * @param PHPStanTypeAlias_Options_Document $options
 	 * 
 	 * @throws Exception if generating json fails
 	 */
@@ -28,7 +28,7 @@ public function toJson(array $options=[]): string;
 	 * 
 	 * @note will set http status code and content type, and echo json
 	 * 
-	 * @param PHPStanTypeAlias_InternalOptions $options
+	 * @param PHPStanTypeAlias_Options_Document $options
 	 */
 	public function sendResponse(array $options=[]): void;
 }
diff --git a/src/interfaces/HasAttributesInterface.php b/src/interfaces/HasAttributesInterface.php
index f42b426b..cfa16bf1 100644
--- a/src/interfaces/HasAttributesInterface.php
+++ b/src/interfaces/HasAttributesInterface.php
@@ -8,9 +8,9 @@ interface HasAttributesInterface {
 	/**
 	 * add key-value pairs to attributes
 	 * 
-	 * @see ResourceObject::$defaults
+	 * @see Validator::$validatorDefaults
 	 * 
-	 * @param PHPStanTypeAlias_InternalOptions $options
+	 * @param PHPStanTypeAlias_Options_Validator $options
 	 */
 	public function addAttribute(string $key, mixed $value, array $options=[]): void;
 }
diff --git a/src/objects/AttributesObject.php b/src/objects/AttributesObject.php
index 86600ffe..6463e07e 100644
--- a/src/objects/AttributesObject.php
+++ b/src/objects/AttributesObject.php
@@ -24,6 +24,8 @@ class AttributesObject extends AbstractObject {
 	/**
 	 * @note if an `id` is set inside $attributes, it is removed from there
 	 *       it is common to find it inside, and not doing so will cause an exception
+	 * 
+	 * @param array<string, mixed> $attributes
 	 */
 	public static function fromArray(array $attributes): static {
 		unset($attributes['id']);
diff --git a/src/objects/ErrorObject.php b/src/objects/ErrorObject.php
index cd47138c..23e07c75 100644
--- a/src/objects/ErrorObject.php
+++ b/src/objects/ErrorObject.php
@@ -29,8 +29,8 @@ class ErrorObject extends AbstractObject implements HasLinksInterface, HasMetaIn
 	/** @var array{pointer?: string, parameter?: string, header?: string} */
 	protected array $source = [];
 	protected MetaObject $meta;
-	/** @var PHPStanTypeAlias_InternalOptions */
-	protected static array $defaults = [
+	/** @var PHPStanTypeAlias_DefaultOptions_ErrorObject */
+	protected static array $errorObjectDefaults = [
 		/**
 		 * add the trace of exceptions when adding exceptions
 		 * in some cases it might be handy to disable if traces are too big
@@ -71,10 +71,10 @@ public function __construct(
 	 */
 	
 	/**
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ErrorObject::$defaults}
+	 * @param PHPStanTypeAlias_Options_ErrorObject $options {@see ErrorObject::$errorObjectDefaults}
 	 */
 	public static function fromException(\Throwable $exception, array $options=[]): static {
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$errorObjectDefaults, ...$options];
 		
 		$errorObject = new static();
 		
diff --git a/src/objects/LinkObject.php b/src/objects/LinkObject.php
index 5a13d2fb..7fbb4fdb 100644
--- a/src/objects/LinkObject.php
+++ b/src/objects/LinkObject.php
@@ -152,12 +152,7 @@ public function toArray(): array {
 			$array['type'] = $this->type;
 		}
 		if ($this->hreflang !== []) {
-			if (count($this->hreflang) === 1) {
-				$array['hreflang'] = $this->hreflang[0];
-			}
-			else {
-				$array['hreflang'] = $this->hreflang;
-			}
+			$array['hreflang'] = $this->getHrefLanguages();
 		}
 		if (isset($this->describedby) && $this->describedby->isEmpty() === false) {
 			$array['describedby'] = $this->describedby->toArray();
@@ -168,4 +163,11 @@ public function toArray(): array {
 		
 		return $array;
 	}
+	
+	/**
+	 * @return string|string[]
+	 */
+	private function getHrefLanguages(): string|array {
+		return (count($this->hreflang) === 1) ? $this->hreflang[0] : $this->hreflang;
+	}
 }
diff --git a/src/objects/LinksObject.php b/src/objects/LinksObject.php
index 3485f309..e8eb7595 100644
--- a/src/objects/LinksObject.php
+++ b/src/objects/LinksObject.php
@@ -16,7 +16,7 @@
  * that might break the class since we use `new static()`
  */
 class LinksObject extends AbstractObject {
-	/** @var array<string, string|LinkObject> */
+	/** @var array<string, string|LinkObject|null> */
 	protected array $links = [];
 	
 	/**
@@ -37,6 +37,7 @@ public static function fromArray(array $links): LinksObject {
 	}
 	
 	public static function fromObject(object $links): LinksObject {
+		/** @var array<string, ?string> $array */
 		$array = Converter::objectToArray($links);
 		
 		return static::fromArray($array);
diff --git a/src/objects/RelationshipObject.php b/src/objects/RelationshipObject.php
index e44ece9a..4c74e41c 100644
--- a/src/objects/RelationshipObject.php
+++ b/src/objects/RelationshipObject.php
@@ -45,8 +45,6 @@ public function __construct(
 	 * @param  CollectionDocument|ResourceInterface|ResourceInterface[]|null $relation 
 	 * @param  array<string, ?string>                                        $links
 	 * @param  array<string, mixed>                                          $meta
-	 * 
-	 * @throws InputException if $relation is not one of the supported formats
 	 */
 	public static function fromAnything(
 		array|CollectionDocument|ResourceInterface|null $relation,
@@ -66,9 +64,6 @@ public static function fromAnything(
 		elseif ($relation === null) {
 			$relationshipObject = new RelationshipObject(RelationshipTypeEnum::ToOne);
 		}
-		else {
-			throw new InputException('unknown format of relation "'.get_debug_type($relation).'"');
-		}
 		
 		return $relationshipObject;
 	}
@@ -122,14 +117,14 @@ public static function fromCollectionDocument(CollectionDocument $collectionDocu
 	}
 	
 	/**
-	 * @param array $meta if given a LinkObject is added, otherwise a link string is added
+	 * @param array<string, mixed> $meta if given a LinkObject is added, otherwise a link string is added
 	 */
 	public function setSelfLink(string $href, array $meta=[]): void {
 		$this->addLink('self', $href, $meta);
 	}
 	
 	/**
-	 * @param array $meta if given a LinkObject is added, otherwise a link string is added
+	 * @param array<string, mixed> $meta if given a LinkObject is added, otherwise a link string is added
 	 */
 	public function setRelatedLink(string $href, array $meta=[]): void {
 		$this->addLink('related', $href, $meta);
@@ -316,6 +311,7 @@ public function getNestedContainedResourceObjects(): array {
 		$resourceObjects = [];
 		
 		foreach ($resources as $resource) {
+			// @phpstan-ignore instanceof.alwaysTrue, identical.alwaysFalse (we _can_ have both ResourceObject and ResourceIdentifierObject here)
 			if ($resource->getResource() instanceof ResourceObject === false) {
 				continue;
 			}
diff --git a/src/objects/RelationshipsObject.php b/src/objects/RelationshipsObject.php
index 537f909c..f5e02a0e 100644
--- a/src/objects/RelationshipsObject.php
+++ b/src/objects/RelationshipsObject.php
@@ -29,7 +29,7 @@ class RelationshipsObject extends AbstractObject implements RecursiveResourceCon
 	 */
 	public function add(
 		string $key,
-		$relation,
+		array|CollectionDocument|ResourceInterface|null $relation,
 		array $links=[],
 		array $meta=[],
 	): RelationshipObject {
diff --git a/src/objects/ResourceIdentifierObject.php b/src/objects/ResourceIdentifierObject.php
index 5f09cd4d..b45be053 100644
--- a/src/objects/ResourceIdentifierObject.php
+++ b/src/objects/ResourceIdentifierObject.php
@@ -112,7 +112,7 @@ public function setMetaObject(MetaObject $metaObject): void {
 	 */
 	public static function fromResourceObject(ResourceObject $resourceObject): static {
 		if ($resourceObject->hasIdentification() === false) {
-			throw new InputException('resource has no identification yet<');
+			throw new InputException('resource has no identification yet');
 		}
 		
 		$resourceIdentifierObject = new static($resourceObject->type, $resourceObject->primaryId());
diff --git a/src/objects/ResourceObject.php b/src/objects/ResourceObject.php
index 8f115f59..c42b4697 100644
--- a/src/objects/ResourceObject.php
+++ b/src/objects/ResourceObject.php
@@ -23,8 +23,8 @@ class ResourceObject extends ResourceIdentifierObject implements HasAttributesIn
 	
 	protected AttributesObject $attributes;
 	protected RelationshipsObject $relationships;
-	/** @var PHPStanTypeAlias_InternalOptions */
-	protected static array $defaults = [
+	/** @var PHPStanTypeAlias_DefaultOptions_Validator */
+	protected static array $resourceObjectDefaults = [
 		/**
 		 * blocks 'type' as a keyword inside attributes or relationships
 		 * the specification doesn't allow this as 'type' is already set at the root of a resource
@@ -42,8 +42,8 @@ class ResourceObject extends ResourceIdentifierObject implements HasAttributesIn
 	 *       and if $id is null, it is filled with that value
 	 *       it is common to find it inside, and not doing so will cause an exception
 	 * 
-	 * @param array<string, mixed>             $attributes
-	 * @param PHPStanTypeAlias_InternalOptions $options    {@see ResourceObject::$defaults}
+	 * @param array<string, mixed>              $attributes
+	 * @param PHPStanTypeAlias_Options_Validator $options    {@see ResourceObject::$resourceObjectDefaults}
 	 */
 	public static function fromArray(array $attributes, ?string $type=null, string|int|null $id=null, array $options=[]): static {
 		if (isset($attributes['id'])) {
@@ -61,7 +61,7 @@ public static function fromArray(array $attributes, ?string $type=null, string|i
 	}
 	
 	/**
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ResourceObject::$defaults}
+	 * @param PHPStanTypeAlias_Options_Validator $options {@see ResourceObject::$resourceObjectDefaults}
 	 */
 	public static function fromObject(object $attributes, ?string $type=null, string|int|null $id=null, array $options=[]): static {
 		$array = Converter::objectToArray($attributes);
@@ -72,10 +72,10 @@ public static function fromObject(object $attributes, ?string $type=null, string
 	/**
 	 * add key-value pairs to attributes
 	 * 
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ResourceObject::$defaults}
+	 * @param PHPStanTypeAlias_Options_Validator $options {@see ResourceObject::$resourceObjectDefaults}
 	 */
 	public function add(string $key, mixed $value, array $options=[]): void {
-		$options = [...self::$defaults, ...$options];
+		$options = [...self::$resourceObjectDefaults, ...$options];
 		
 		if (isset($this->attributes) === false) {
 			$this->attributes = new AttributesObject();
@@ -90,7 +90,7 @@ public function add(string $key, mixed $value, array $options=[]): void {
 	 * @param CollectionDocument|ResourceInterface|ResourceInterface[]|null $relation 
 	 * @param array<string, ?string>                                        $links
 	 * @param array<string, mixed>                                          $meta
-	 * @param PHPStanTypeAlias_InternalOptions                              $options {@see ResourceObject::$defaults}
+	 * @param PHPStanTypeAlias_Options_Validator                            $options {@see ResourceObject::$resourceObjectDefaults}
 	 */
 	public function addRelationship(
 		string $key,
@@ -118,7 +118,7 @@ public function setSelfLink(string $href, array $meta=[]): void {
 	 */
 	
 	/**
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ResourceObject::$defaults}
+	 * @param PHPStanTypeAlias_Options_Validator $options {@see ResourceObject::$resourceObjectDefaults}
 	 */
 	public function setAttributesObject(AttributesObject $attributesObject, array $options=[]): void {
 		$newKeys = $attributesObject->getKeys();
@@ -129,7 +129,7 @@ public function setAttributesObject(AttributesObject $attributesObject, array $o
 	}
 	
 	/**
-	 * @param PHPStanTypeAlias_InternalOptions $options {@see ResourceObject::$defaults}
+	 * @param PHPStanTypeAlias_Options_Validator $options {@see ResourceObject::$resourceObjectDefaults}
 	 * 
 	 * @throws DuplicateException if the resource is contained as a resource in the relationship
 	 */
@@ -185,7 +185,7 @@ public function hasIdentifierPropertiesOnly(): bool {
 	 */
 	
 	public function addAttribute(string $key, mixed $value, array $options=[]): void {
-		$this->add($key, $value);
+		$this->add($key, $value, $options);
 	}
 	
 	/**
diff --git a/src/profiles/CursorPaginationProfile.php b/src/profiles/CursorPaginationProfile.php
index 75825210..72c31c0e 100644
--- a/src/profiles/CursorPaginationProfile.php
+++ b/src/profiles/CursorPaginationProfile.php
@@ -6,6 +6,7 @@
 
 use alsvanzelf\jsonapi\ResourceDocument;
 use alsvanzelf\jsonapi\enums\DocumentLevelEnum;
+use alsvanzelf\jsonapi\exceptions\Exception;
 use alsvanzelf\jsonapi\exceptions\InputException;
 use alsvanzelf\jsonapi\interfaces\HasLinksInterface;
 use alsvanzelf\jsonapi\interfaces\HasMetaInterface;
@@ -56,10 +57,10 @@ class CursorPaginationProfile implements ProfileInterface {
 	/**
 	 * set links to paginate the data using cursors of the paginated data
 	 * 
-	 * @param PaginableInterface $paginable a CollectionDocument or RelationshipObject
+	 * @param PaginableInterface & HasLinksInterface $paginable a CollectionDocument or RelationshipObject
 	 */
 	public function setLinks(
-		PaginableInterface $paginable,
+		PaginableInterface & HasLinksInterface $paginable,
 		string $baseOrCurrentUrl,
 		string $firstCursor,
 		string $lastCursor,
@@ -71,32 +72,32 @@ public function setLinks(
 	}
 	
 	/**
-	 * @param PaginableInterface $paginable a CollectionDocument or RelationshipObject
+	 * @param PaginableInterface & HasLinksInterface $paginable a CollectionDocument or RelationshipObject
 	 */
-	public function setLinksFirstPage(PaginableInterface $paginable, string $baseOrCurrentUrl, string $lastCursor): void {
+	public function setLinksFirstPage(PaginableInterface & HasLinksInterface $paginable, string $baseOrCurrentUrl, string $lastCursor): void {
 		$this->setPaginationLinkObjectsWithoutPrevious($paginable, $baseOrCurrentUrl, $lastCursor);
 	}
 	
 	/**
-	 * @param PaginableInterface $paginable a CollectionDocument or RelationshipObject
+	 * @param PaginableInterface & HasLinksInterface $paginable a CollectionDocument or RelationshipObject
 	 */
-	public function setLinksLastPage(PaginableInterface $paginable, string $baseOrCurrentUrl, string $firstCursor): void {
+	public function setLinksLastPage(PaginableInterface & HasLinksInterface $paginable, string $baseOrCurrentUrl, string $firstCursor): void {
 		$this->setPaginationLinkObjectsWithoutNext($paginable, $baseOrCurrentUrl, $firstCursor);
 	}
 	
 	/**
 	 * set the cursor of a specific resource to allow pagination after or before this resource
 	 */
-	public function setCursor(ResourceInterface $resource, string $cursor): void {
+	public function setCursor(ResourceInterface & HasMetaInterface $resource, string $cursor): void {
 		$this->setItemMeta($resource, $cursor);
 	}
 	
 	/**
 	 * set count(s) to tell about the (estimated) total size
 	 * 
-	 * @param PaginableInterface $paginable a CollectionDocument or RelationshipObject
+	 * @param PaginableInterface & HasMetaInterface $paginable a CollectionDocument or RelationshipObject
 	 */
-	public function setCount(PaginableInterface $paginable, ?int $exactTotal=null, ?int $bestGuessTotal=null) {
+	public function setCount(PaginableInterface & HasMetaInterface $paginable, ?int $exactTotal=null, ?int $bestGuessTotal=null): void {
 		$this->setPaginationMeta($paginable, $exactTotal, $bestGuessTotal);
 	}
 	
@@ -114,7 +115,7 @@ public function generatePreviousLink(string $baseOrCurrentUrl, string $beforeCur
 	/**
 	 * helper to get generate a correct page[after] link, use to apply manually
 	 */
-	public function generateNextLink($baseOrCurrentUrl, $afterCursor) {
+	public function generateNextLink(string $baseOrCurrentUrl, string $afterCursor): string {
 		return $this->setQueryParameter($baseOrCurrentUrl, 'page[after]', $afterCursor);
 	}
 	
@@ -137,15 +138,15 @@ public function setPaginationLinkObjects(
 		$paginable->addLinkObject('next', $nextLinkObject);
 	}
 	
-	public function setPaginationLinkObjectsWithoutNext(PaginableInterface $paginable, string $baseOrCurrentUrl, string $firstCursor): void {
+	public function setPaginationLinkObjectsWithoutNext(PaginableInterface & HasLinksInterface $paginable, string $baseOrCurrentUrl, string $firstCursor): void {
 		$this->setPaginationLinkObjects($paginable, new LinkObject($this->generatePreviousLink($baseOrCurrentUrl, $firstCursor)), new LinkObject());
 	}
 	
-	public function setPaginationLinkObjectsWithoutPrevious(PaginableInterface $paginable, string $baseOrCurrentUrl, string $lastCursor): void {
+	public function setPaginationLinkObjectsWithoutPrevious(PaginableInterface & HasLinksInterface $paginable, string $baseOrCurrentUrl, string $lastCursor): void {
 		$this->setPaginationLinkObjects($paginable, new LinkObject(), new LinkObject($this->generateNextLink($baseOrCurrentUrl, $lastCursor)));
 	}
 	
-	public function setPaginationLinkObjectsExplicitlyEmpty(PaginableInterface $paginable): void {
+	public function setPaginationLinkObjectsExplicitlyEmpty(PaginableInterface & HasLinksInterface $paginable): void {
 		$this->setPaginationLinkObjects($paginable, new LinkObject(), new LinkObject());
 	}
 	
@@ -304,9 +305,15 @@ public function getRangePaginationNotSupportedErrorObject(?string $genericTitle=
 	
 	/**
 	 * add or adjust a key in the query string of a url
+	 * 
+	 * @throws InputException on missing or broken query parameters inside $url
 	 */
 	private function setQueryParameter(string $url, string $key, string $value): string {
-		$originalQuery     = parse_url($url, PHP_URL_QUERY);
+		$originalQuery = parse_url($url, PHP_URL_QUERY);
+		if ($originalQuery === null || $originalQuery === false) {
+			throw new InputException('missing or broken query parameters in url');
+		}
+		
 		$decodedQuery      = urldecode($originalQuery);
 		$originalIsEncoded = ($decodedQuery !== $originalQuery);
 		
diff --git a/tests/CollectionDocumentTest.php b/tests/CollectionDocumentTest.php
index b05004ab..fddf3009 100644
--- a/tests/CollectionDocumentTest.php
+++ b/tests/CollectionDocumentTest.php
@@ -10,7 +10,7 @@
 use alsvanzelf\jsonapi\exceptions\InputException;
 use alsvanzelf\jsonapi\objects\ResourceObject;
 
-class CollectionDocumentTest extends TestCase {
+final class CollectionDocumentTest extends TestCase {
 	public function testConstructor_NoResources(): void {
 		$document = new CollectionDocument();
 		
@@ -101,7 +101,7 @@ public function testSetPaginationLinks_HappyPath(): void {
 	}
 	
 	#[DataProvider('dataProviderSetPaginationLinks_IndividualLinks')]
-	public function testSetPaginationLinks_IndividualLinks($key, $previous, $next, $first, $last): void {
+	public function testSetPaginationLinks_IndividualLinks(?string $key, ?string $previous, ?string $next, ?string $first, ?string $last): void {
 		$document = new CollectionDocument();
 		
 		$document->setPaginationLinks($previous, $next, $first, $last);
@@ -119,14 +119,15 @@ public function testSetPaginationLinks_IndividualLinks($key, $previous, $next, $
 		}
 	}
 	
-	public static function dataProviderSetPaginationLinks_IndividualLinks() {
-		return [
-			['prev',  'https://jsonapi.org', null, null, null],
-			['next',  null, 'https://jsonapi.org', null, null],
-			['first', null, null, 'https://jsonapi.org', null],
-			['last',  null, null, null, 'https://jsonapi.org'],
-			[null,    null, null, null, null],
-		];
+	/**
+	 * @return \Iterator<(int | string), array{(string | null), (string | null), (string | null), (string | null), (string | null)}>
+	 */
+	public static function dataProviderSetPaginationLinks_IndividualLinks(): \Iterator {
+		yield ['prev',  'https://jsonapi.org', null, null, null];
+		yield ['next',  null, 'https://jsonapi.org', null, null];
+		yield ['first', null, null, 'https://jsonapi.org', null];
+		yield ['last',  null, null, null, 'https://jsonapi.org'];
+		yield [null,    null, null, null, null];
 	}
 	
 	public function testAddResource_HappyPath(): void {
diff --git a/tests/ConverterTest.php b/tests/ConverterTest.php
index d2af386a..8eeb973f 100644
--- a/tests/ConverterTest.php
+++ b/tests/ConverterTest.php
@@ -10,9 +10,10 @@
 use alsvanzelf\jsonapi\interfaces\ProfileInterface;
 use alsvanzelf\jsonapi\objects\AttributesObject;
 use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-class ConverterTest extends TestCase {
+final class ConverterTest extends TestCase {
 	public function testObjectToArray_HappyPath(): void {
 		$object = new \stdClass();
 		$object->foo = 'bar';
@@ -29,10 +30,10 @@ public function testObjectToArray_HappyPath(): void {
 	
 	public function testObjectToArray_MethodsAndPrivateProperties(): void {
 		$object = new class {
-			public $foo = 'bar';
-			public $baz = 42;
-			private $secret = 'value'; // @phpstan-ignore property.onlyWritten
-			public function method() {}
+			public string $foo = 'bar';
+			public int $baz = 42;
+			private string $secret = 'value'; // @phpstan-ignore property.onlyWritten
+			public function method(): void {}
 		};
 		
 		$array = Converter::objectToArray($object);
@@ -58,50 +59,43 @@ public function testObjectToArray_FromInternalObject(): void {
 	}
 	
 	#[DataProvider('dataProviderCamelCaseToWords_HappyPath')]
-	public function testCamelCaseToWords_HappyPath($camelCase, $expectedOutput): void {
+	public function testCamelCaseToWords_HappyPath(string $camelCase, string $expectedOutput): void {
 		parent::assertSame($expectedOutput, Converter::camelCaseToWords($camelCase));
 	}
 	
-	public static function dataProviderCamelCaseToWords_HappyPath() {
-		return [
-			['value',         'value'],
-			['camelValue',    'camel Value'],
-			['TitleValue',    'Title Value'],
-			['VALUE',         'VALUE'],
-			['eclipseRCPExt', 'eclipse RCP Ext'],
-		];
-	}
-	
 	/**
-	 * @group Extensions
-	 * @group Profiles
+	 * @return \Iterator<(int | string), array{string, string}>
 	 */
+	public static function dataProviderCamelCaseToWords_HappyPath(): \Iterator {
+		yield ['value',         'value'];
+		yield ['camelValue',    'camel Value'];
+		yield ['TitleValue',    'Title Value'];
+		yield ['VALUE',         'VALUE'];
+		yield ['eclipseRCPExt', 'eclipse RCP Ext'];
+	}
+	
+	#[Group('Extensions')]
+	#[Group('Profiles')]
 	public function testPrepareContentType_HappyPath(): void {
 		parent::assertSame(ContentTypeEnum::Official->value, Converter::prepareContentType(ContentTypeEnum::Official, [], []));
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testPrepareContentType_WithExtensionStringLink(): void {
 		$extension = parent::createConfiguredStub(ExtensionInterface::class, ['getOfficialLink' => 'bar']);
 		
 		parent::assertSame(ContentTypeEnum::Official->value.'; ext="bar"', Converter::prepareContentType(ContentTypeEnum::Official, [$extension], []));
 	}
 	
-	/**
-	 * @group Profiles
-	 */
+	#[Group('Profiles')]
 	public function testPrepareContentType_WithProfileStringLink(): void {
 		$profile = parent::createConfiguredStub(ProfileInterface::class, ['getOfficialLink' => 'bar']);
 		
 		parent::assertSame(ContentTypeEnum::Official->value.'; profile="bar"', Converter::prepareContentType(ContentTypeEnum::Official, [], [$profile]));
 	}
 	
-	/**
-	 * @group Extensions
-	 * @group Profiles
-	 */
+	#[Group('Extensions')]
+	#[Group('Profiles')]
 	public function testPrepareContentType_WithMultipleExtensionsAndProfiles(): void {
 		$extension1 = parent::createConfiguredStub(ExtensionInterface::class, ['getOfficialLink' => 'bar']);
 		$extension2 = parent::createConfiguredStub(ExtensionInterface::class, ['getOfficialLink' => 'baz']);
diff --git a/tests/DocumentTest.php b/tests/DocumentTest.php
index 625088ef..c166f27c 100644
--- a/tests/DocumentTest.php
+++ b/tests/DocumentTest.php
@@ -12,12 +12,13 @@
 use alsvanzelf\jsonapi\interfaces\ExtensionInterface;
 use alsvanzelf\jsonapi\interfaces\ProfileInterface;
 use alsvanzelf\jsonapi\objects\LinkObject;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-class DocumentTest extends TestCase {
-	private object $document;
+final class DocumentTest extends TestCase {
+	private Document $document;
 	
-	public function setUp(): void {
+	protected function setUp(): void {
 		/**
 		 * extending Document to make it non-abstract to test against it
 		 * 
@@ -180,9 +181,7 @@ public function testAddLinkObject_HappyPath(): void {
 		parent::assertSame('https://jsonapi.org', $array['links']['foo']['href']);
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testApplyExtension_HappyPath(): void {
 		$extension = parent::createConfiguredStub(ExtensionInterface::class, [
 			'getNamespace'    => 'test',
@@ -215,9 +214,7 @@ public function testApplyExtension_HappyPath(): void {
 		parent::assertSame('application/vnd.api+json; ext="https://jsonapi.org/extension"', $array['links']['self']['type']);
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testApplyExtension_InvalidNamespace(): void {
 		$extension = parent::createConfiguredStub(ExtensionInterface::class, ['getNamespace' => 'foo-bar']);
 		
@@ -227,9 +224,7 @@ public function testApplyExtension_InvalidNamespace(): void {
 		$this->document->applyExtension($extension);
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testApplyExtension_ConflictingNamespace(): void {
 		$extension1 = parent::createConfiguredStub(ExtensionInterface::class, ['getNamespace' => 'foo']);
 		$this->document->applyExtension($extension1);
@@ -245,9 +240,7 @@ public function testApplyExtension_ConflictingNamespace(): void {
 		$this->document->applyExtension($extension3);
 	}
 	
-	/**
-	 * @group Profiles
-	 */
+	#[Group('Profiles')]
 	public function testApplyProfile_HappyPath(): void {
 		$profile = parent::createConfiguredStub(ProfileInterface::class, ['getOfficialLink' => 'https://jsonapi.org/profile']);
 		
@@ -312,6 +305,15 @@ public function testToJson_InvalidUtf8(): void {
 		$this->document->toJson($options);
 	}
 	
+	public function testToJson_InvalidUtf8CustomException(): void {
+		$options = ['array' => ['foo' => "\xB1\x31"], 'encodeOptions' => JSON_UNESCAPED_SLASHES|JSON_UNESCAPED_UNICODE];
+		
+		$this->expectException(Exception::class);
+		$this->expectExceptionMessage('failed to encode json: Malformed UTF-8 characters, possibly incorrectly encoded');
+		
+		$this->document->toJson($options);
+	}
+	
 	public function testJsonSerialize_HappyPath(): void {
 		$this->document->addMeta('foo', 'bar');
 		
diff --git a/tests/ErrorsDocumentTest.php b/tests/ErrorsDocumentTest.php
index c7952517..e19a0eeb 100644
--- a/tests/ErrorsDocumentTest.php
+++ b/tests/ErrorsDocumentTest.php
@@ -9,7 +9,7 @@
 use alsvanzelf\jsonapi\ErrorsDocument;
 use alsvanzelf\jsonapi\objects\ErrorObject;
 
-class ErrorsDocumentTest extends TestCase {
+final class ErrorsDocumentTest extends TestCase {
 	public function testFromException_HappyPath(): void {
 		$document = ErrorsDocument::fromException(new \Exception('foo', 42));
 		
@@ -120,19 +120,20 @@ public function testDetermineHttpStatusCode_HappyPath(int $expectedAdvisedErrorC
 		parent::assertSame($expectedAdvisedErrorCode, $advisedErrorCode);
 	}
 	
-	public static function dataProviderDetermineHttpStatusCode_HappyPath() {
-		return [
-			[422, [422]],
-			[422, [422, 422]],
-			[400, [422, 404]],
-			[400, [400]],
-			[501, [501]],
-			[501, [501, 501]],
-			[500, [501, 503]],
-			[500, [422, 404, 501, 503]],
-			[500, [500]],
-			[302, [302]],
-		];
+	/**
+	 * @return \Iterator<(int | string), array{int, non-empty-array<int>}>
+	 */
+	public static function dataProviderDetermineHttpStatusCode_HappyPath(): \Iterator {
+		yield [422, [422]];
+		yield [422, [422, 422]];
+		yield [400, [422, 404]];
+		yield [400, [400]];
+		yield [501, [501]];
+		yield [501, [501, 501]];
+		yield [500, [501, 503]];
+		yield [500, [422, 404, 501, 503]];
+		yield [500, [500]];
+		yield [302, [302]];
 	}
 	
 	public function testDetermineHttpStatusCode_Override(): void {
diff --git a/tests/ExampleOutputTest.php b/tests/ExampleOutputTest.php
index 75a699f0..260efe26 100644
--- a/tests/ExampleOutputTest.php
+++ b/tests/ExampleOutputTest.php
@@ -4,23 +4,23 @@
 
 namespace alsvanzelf\jsonapiTests;
 
+use alsvanzelf\jsonapi\interfaces\DocumentInterface;
 use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-/**
- * @group OutputOnly
- */
-class ExampleOutputTest extends TestCase {
-	private static $defaults = [
+#[Group('OutputOnly')]
+final class ExampleOutputTest extends TestCase {
+	/** @var PHPStanTypeAlias_Options_Document */
+	private static array $defaults = [
 		'prettyPrint' => true,
 	];
 	
 	#[DataProvider('dataProviderTestOutput')]
-	public function testOutput($generator, $expectedJson, array $options=[], $testName=null): void {
-		$options = [...self::$defaults, ...$options];
-		
-		$document   = $generator::createJsonapiDocument();
-		$actualJson = $document->toJson($options);
+	public function testOutput(object $generator, ?string $expectedJson, ?string $testName): void {
+		/** @var DocumentInterface $document */
+		$document   = $generator::createJsonapiDocument(); // @phpstan-ignore staticMethod.notFound
+		$actualJson = $document->toJson(self::$defaults);
 		
 		// adhere to editorconfig
 		$actualJson = str_replace('    ', "\t", $actualJson).PHP_EOL;
@@ -35,8 +35,18 @@ public function testOutput($generator, $expectedJson, array $options=[], $testNa
 		parent::assertSame($expectedJson, $actualJson);
 	}
 	
-	public static function dataProviderTestOutput() {
+	/**
+	 * @return array<string, array{
+	 *         0: object,
+	 *         1: ?string,
+	 *         2: string
+	 * }>
+	 */
+	public static function dataProviderTestOutput(): array {
 		$directories = glob(__DIR__.'/example_output/*', GLOB_ONLYDIR);
+		if ($directories === false) {
+			throw new \Exception('failed to fetch example output');
+		}
 		
 		$testCases = [];
 		foreach ($directories as $directory) {
@@ -47,16 +57,15 @@ public static function dataProviderTestOutput() {
 			
 			$generator    = new $className;
 			$expectedJson = null;
-			$options      = [];
 			
 			if (file_exists($directory.'/'.$testName.'.json')) {
 				$expectedJson = file_get_contents($directory.'/'.$testName.'.json');
-			}
-			if (file_exists($directory.'/options.txt')) {
-				$options = json_decode(file_get_contents($directory.'/options.txt'), associative: true, flags: JSON_THROW_ON_ERROR);
+				if ($expectedJson === false) {
+					throw new \Exception('something went wrong fetching expected output');
+				}
 			}
 			
-			$testCases[$testName] = [$generator, $expectedJson, $options, $testName];
+			$testCases[$testName] = [$generator, $expectedJson, $testName];
 		}
 		
 		return $testCases;
diff --git a/tests/MetaDocumentTest.php b/tests/MetaDocumentTest.php
index 1db500d8..7cfe65a2 100644
--- a/tests/MetaDocumentTest.php
+++ b/tests/MetaDocumentTest.php
@@ -7,7 +7,7 @@
 use alsvanzelf\jsonapi\MetaDocument;
 use PHPUnit\Framework\TestCase;
 
-class MetaDocumentTest extends TestCase {
+final class MetaDocumentTest extends TestCase {
 	public function testConstructor_NoMeta(): void {
 		$document = new MetaDocument();
 		
diff --git a/tests/ResourceDocumentTest.php b/tests/ResourceDocumentTest.php
index 144d574c..d903272e 100644
--- a/tests/ResourceDocumentTest.php
+++ b/tests/ResourceDocumentTest.php
@@ -6,6 +6,7 @@
 
 use alsvanzelf\jsonapi\ResourceDocument;
 use alsvanzelf\jsonapi\enums\DocumentLevelEnum;
+use alsvanzelf\jsonapi\enums\RelationshipTypeEnum;
 use alsvanzelf\jsonapi\exceptions\Exception;
 use alsvanzelf\jsonapi\exceptions\InputException;
 use alsvanzelf\jsonapi\interfaces\ExtensionInterface;
@@ -14,9 +15,10 @@
 use alsvanzelf\jsonapi\objects\RelationshipsObject;
 use alsvanzelf\jsonapi\objects\ResourceIdentifierObject;
 use alsvanzelf\jsonapi\objects\ResourceObject;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-class ResourceDocumentTest extends TestCase {
+final class ResourceDocumentTest extends TestCase {
 	public function testConstructor_NoResource(): void {
 		$document = new ResourceDocument();
 		
@@ -61,9 +63,7 @@ public function testAdd_IdentifierOnlyObject(): void {
 		$document->add('foo', 'bar');
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testAdd_BlocksExtensionMembersViaRegularAdd(): void {
 		$document = new ResourceDocument();
 		$document->applyExtension(parent::createConfiguredStub(ExtensionInterface::class, ['getNamespace' => 'test']));
@@ -100,6 +100,66 @@ public function testAddRelationship_DoNotIncludeContainedResources(): void {
 		parent::assertArrayNotHasKey('included', $array);
 	}
 	
+	public function testAddRelationship_IdentifierOnlyObject(): void {
+		$document = new ResourceDocument();
+		$document->setPrimaryResource(new ResourceIdentifierObject('user', 42));
+		
+		$this->expectException(Exception::class);
+		$this->expectExceptionMessage('the resource is an identifier-only object');
+		
+		$document->addRelationship('foo', null);
+	}
+	
+	public function testAddLink_IdentifierOnlyObject(): void {
+		$document = new ResourceDocument();
+		$document->setPrimaryResource(new ResourceIdentifierObject('user', 42));
+		
+		$this->expectException(Exception::class);
+		$this->expectExceptionMessage('the resource is an identifier-only object');
+		
+		$document->addLink('foo', null);
+	}
+	
+	public function testSetSelfLink_IdentifierOnlyObject(): void {
+		$document = new ResourceDocument();
+		$document->setPrimaryResource(new ResourceIdentifierObject('user', 42));
+		
+		$this->expectException(Exception::class);
+		$this->expectExceptionMessage('the resource is an identifier-only object');
+		
+		$document->setSelfLink('https://jsonapi.org');
+	}
+	
+	public function testSetAttributesObject_IdentifierOnlyObject(): void {
+		$document = new ResourceDocument();
+		$document->setPrimaryResource(new ResourceIdentifierObject('user', 42));
+		
+		$this->expectException(Exception::class);
+		$this->expectExceptionMessage('the resource is an identifier-only object');
+		
+		$document->setAttributesObject(new AttributesObject());
+	}
+	
+	public function testAddRelationshipObject_IdentifierOnlyObject(): void {
+		$document = new ResourceDocument();
+		$document->setPrimaryResource(new ResourceIdentifierObject('user', 42));
+		
+		$this->expectException(Exception::class);
+		$this->expectExceptionMessage('the resource is an identifier-only object');
+		
+		$document->addRelationshipObject('foo', new RelationshipObject(RelationshipTypeEnum::ToOne));
+	}
+	
+	public function testSetRelationshipsObject_IdentifierOnlyObject(): void {
+		$document = new ResourceDocument();
+		$document->setPrimaryResource(new ResourceIdentifierObject('user', 42));
+		
+		$this->expectException(Exception::class);
+		$this->expectExceptionMessage('the resource is an identifier-only object');
+		
+		$document->setRelationshipsObject(new RelationshipsObject());
+	}
+	
 	public function testAddMeta_HappyPath(): void {
 		$document = new ResourceDocument();
 		$document->addMeta('foo', 'root', DocumentLevelEnum::Root);
@@ -110,18 +170,12 @@ public function testAddMeta_HappyPath(): void {
 		
 		parent::assertArrayHasKey('meta', $array);
 		parent::assertArrayHasKey('data', $array);
-		parent::assertArrayHasKey('meta', $array['data']);
 		parent::assertArrayHasKey('jsonapi', $array);
+		parent::assertArrayHasKey('meta', $array['data']);
 		parent::assertArrayHasKey('meta', $array['jsonapi']);
-		parent::assertArrayHasKey('foo', $array['meta']);
-		parent::assertArrayHasKey('bar', $array['data']['meta']);
-		parent::assertArrayHasKey('baz', $array['jsonapi']['meta']);
-		parent::assertCount(1, $array['meta']);
-		parent::assertCount(1, $array['data']['meta']);
-		parent::assertCount(1, $array['jsonapi']['meta']);
-		parent::assertSame('root', $array['meta']['foo']);
-		parent::assertSame('resource', $array['data']['meta']['bar']);
-		parent::assertSame('jsonapi', $array['jsonapi']['meta']['baz']);
+		parent::assertSame(['foo' => 'root'], $array['meta']);
+		parent::assertSame(['bar' => 'resource'], $array['data']['meta']);
+		parent::assertSame(['baz' => 'jsonapi'], $array['jsonapi']['meta']);
 	}
 	
 	public function testAddMeta_RecreateJsonapiObject(): void {
diff --git a/tests/SeparateProcessTest.php b/tests/SeparateProcessTest.php
index 2dc68ce1..98820827 100644
--- a/tests/SeparateProcessTest.php
+++ b/tests/SeparateProcessTest.php
@@ -8,15 +8,14 @@
 use alsvanzelf\jsonapi\enums\ContentTypeEnum;
 use alsvanzelf\jsonapi\interfaces\ExtensionInterface;
 use alsvanzelf\jsonapi\interfaces\ProfileInterface;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-/**
- * @group SeparateProcess
- */
-class SeparateProcessTest extends TestCase {
-	private object $document;
+#[Group('SeparateProcess')]
+final class SeparateProcessTest extends TestCase {
+	private Document $document;
 	
-	public function setUp(): void {
+	protected function setUp(): void {
 		/**
 		 * extending Document to make it non-abstract to test against it
 		 * 
@@ -26,9 +25,6 @@ public function setUp(): void {
 		$this->document = new class extends Document {};
 	}
 	
-	/**
-	 * @runInSeparateProcess
-	 */
 	public function testSendResponse_HappyPath(): void {
 		ob_start();
 		$this->document->sendResponse();
@@ -37,9 +33,6 @@ public function testSendResponse_HappyPath(): void {
 		parent::assertSame('{"jsonapi":{"version":"1.1"}}', $output);
 	}
 	
-	/**
-	 * @runInSeparateProcess
-	 */
 	public function testSendResponse_NoContent(): void {
 		$this->document->setHttpStatusCode(204);
 		
@@ -51,9 +44,6 @@ public function testSendResponse_NoContent(): void {
 		parent::assertSame(204, http_response_code());
 	}
 	
-	/**
-	 * @runInSeparateProcess
-	 */
 	public function testSendResponse_ContentTypeHeader(): void {
 		if (extension_loaded('xdebug') === false) {
 			parent::markTestSkipped('can not run without xdebug');
@@ -83,10 +73,7 @@ public function testSendResponse_ContentTypeHeader(): void {
 		parent::assertSame(['Content-Type: '.ContentTypeEnum::Jsonp->value], xdebug_get_headers());
 	}
 	
-	/**
-	 * @runInSeparateProcess
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testSendResponse_ContentTypeHeaderWithExtensions(): void {
 		if (extension_loaded('xdebug') === false) {
 			parent::markTestSkipped('can not run without xdebug');
@@ -115,10 +102,7 @@ public function testSendResponse_ContentTypeHeaderWithExtensions(): void {
 		parent::assertSame(['Content-Type: '.ContentTypeEnum::Official->value.'; ext="https://jsonapi.org https://jsonapi.org/2"'], xdebug_get_headers());
 	}
 	
-	/**
-	 * @runInSeparateProcess
-	 * @group Profiles
-	 */
+	#[Group('Profiles')]
 	public function testSendResponse_ContentTypeHeaderWithProfiles(): void {
 		if (extension_loaded('xdebug') === false) {
 			parent::markTestSkipped('can not run without xdebug');
@@ -141,9 +125,6 @@ public function testSendResponse_ContentTypeHeaderWithProfiles(): void {
 		parent::assertSame(['Content-Type: '.ContentTypeEnum::Official->value.'; profile="https://jsonapi.org https://jsonapi.org/2"'], xdebug_get_headers());
 	}
 	
-	/**
-	 * @runInSeparateProcess
-	 */
 	public function testSendResponse_StatusCodeHeader(): void {
 		
 		ob_start();
@@ -170,9 +151,6 @@ public function testSendResponse_StatusCodeHeader(): void {
 		parent::assertSame(503, http_response_code());
 	}
 	
-	/**
-	 * @runInSeparateProcess
-	 */
 	public function testSendResponse_CustomJson(): void {
 		$options  = ['json' => '{"foo":42}'];
 		
diff --git a/tests/ValidatorTest.php b/tests/ValidatorTest.php
index 6fa9235d..fdab54c3 100644
--- a/tests/ValidatorTest.php
+++ b/tests/ValidatorTest.php
@@ -13,7 +13,7 @@
 use PHPUnit\Framework\Attributes\DoesNotPerformAssertions;
 use PHPUnit\Framework\TestCase;
 
-class ValidatorTest extends TestCase {
+final class ValidatorTest extends TestCase {
 	#[DoesNotPerformAssertions]
 	public function testClaimUsedFields_HappyPath(): void {
 		$validator = new Validator();
@@ -147,52 +147,55 @@ public function testClaimUsedResourceIdentifier_BlocksDuplicates(): void {
 	
 	#[DoesNotPerformAssertions]
 	#[DataProvider('dataProviderCheckMemberName_HappyPath')]
-	public function testCheckMemberName_HappyPath($memberName): void {
+	public function testCheckMemberName_HappyPath(string $memberName): void {
 		Validator::checkMemberName($memberName);
 	}
 	
-	public static function dataProviderCheckMemberName_HappyPath() {
-		return [
-			['foo'],
-			['f_o'],
-			['f-o'],
-			['42foo'],
-			['42'],
-		];
+	/**
+	 * @return \Iterator<(int | string), array{string}>
+	 */
+	public static function dataProviderCheckMemberName_HappyPath(): \Iterator {
+		yield ['foo'];
+		yield ['f_o'];
+		yield ['f-o'];
+		yield ['42foo'];
+		yield ['42'];
 	}
 	
 	#[DataProvider('dataProviderCheckMemberName_InvalidNames')]
-	public function testCheckMemberName_InvalidNames($memberName): void {
+	public function testCheckMemberName_InvalidNames(string $memberName): void {
 		$this->expectException(InputException::class);
 		
 		Validator::checkMemberName($memberName);
 	}
 	
-	public static function dataProviderCheckMemberName_InvalidNames() {
-		return [
-			['_'],
-			['-'],
-			['foo-'],
-			['-foo'],
-		];
+	/**
+	 * @return \Iterator<(int | string), array{string}>
+	 */
+	public static function dataProviderCheckMemberName_InvalidNames(): \Iterator {
+		yield ['_'];
+		yield ['-'];
+		yield ['foo-'];
+		yield ['-foo'];
 	}
 	
 	#[DataProvider('dataProviderCheckHttpStatusCode_HappyPath')]
-	public function testCheckHttpStatusCode_HappyPath($expectedOutput, $httpStatusCode): void {
+	public function testCheckHttpStatusCode_HappyPath(bool $expectedOutput, int|string $httpStatusCode): void {
 		parent::assertSame($expectedOutput, Validator::checkHttpStatusCode($httpStatusCode));
 	}
 	
-	public static function dataProviderCheckHttpStatusCode_HappyPath() {
-		return [
-			[false, 42],
-			[true,  100],
-			[true,  200],
-			[true,  300],
-			[true,  400],
-			[true,  500],
-			[false, 600],
-			[false, '42'],
-			[true,  '100'],
-		];
+	/**
+	 * @return \Iterator<(int | string), array{bool, (int | string)}>
+	 */
+	public static function dataProviderCheckHttpStatusCode_HappyPath(): \Iterator {
+		yield [false, 42];
+		yield [true,  100];
+		yield [true,  200];
+		yield [true,  300];
+		yield [true,  400];
+		yield [true,  500];
+		yield [false, 600];
+		yield [false, '42'];
+		yield [true,  '100'];
 	}
 }
diff --git a/tests/example_output/ExampleTimestampsProfile.php b/tests/example_output/ExampleTimestampsProfile.php
index 210af099..24fc00e5 100644
--- a/tests/example_output/ExampleTimestampsProfile.php
+++ b/tests/example_output/ExampleTimestampsProfile.php
@@ -14,14 +14,11 @@ public function getOfficialLink(): string {
 		return 'https://jsonapi.org/recommendations/#authoring-profiles';
 	}
 	
-	/**
-	 * @param ResourceInterface&HasAttributesInterface $resource
-	 */
-	public function setTimestamps(ResourceInterface $resource, ?\DateTimeInterface $created=null, ?\DateTimeInterface $updated=null) {
-		if ($resource instanceof HasAttributesInterface === false) {
-			throw new InputException('cannot add attributes to identifier objects');
-		}
-		
+	public function setTimestamps(
+		ResourceInterface & HasAttributesInterface $resource,
+		?\DateTimeInterface $created=null,
+		?\DateTimeInterface $updated=null,
+	): void {
 		$timestamps = [];
 		if ($created !== null) {
 			$timestamps['created'] = $created->format(\DateTime::ISO8601);
diff --git a/tests/example_output/ExampleUser.php b/tests/example_output/ExampleUser.php
index b01edab3..6e607609 100644
--- a/tests/example_output/ExampleUser.php
+++ b/tests/example_output/ExampleUser.php
@@ -5,15 +5,15 @@
 namespace alsvanzelf\jsonapiTests\example_output;
 
 class ExampleUser {
-	public $name;
-	public $heads;
-	public $unknown;
+	public ?string $name = null;
+	public null|int|string $heads = null;
+	public mixed $unknown = null;
 	
 	public function __construct(
-		public $id,
+		public int $id,
 	) {}
 	
-	function getCurrentLocation() {
+	public function getCurrentLocation(): string {
 		return 'Earth';
 	}
 }
diff --git a/tests/example_output/ExampleVersionExtension.php b/tests/example_output/ExampleVersionExtension.php
index dea5cde6..4ac3b719 100644
--- a/tests/example_output/ExampleVersionExtension.php
+++ b/tests/example_output/ExampleVersionExtension.php
@@ -5,7 +5,6 @@
 namespace alsvanzelf\jsonapiTests\example_output;
 
 use alsvanzelf\jsonapi\ResourceDocument;
-use alsvanzelf\jsonapi\exceptions\InputException;
 use alsvanzelf\jsonapi\interfaces\ExtensionInterface;
 use alsvanzelf\jsonapi\interfaces\HasExtensionMembersInterface;
 use alsvanzelf\jsonapi\interfaces\ResourceInterface;
@@ -19,11 +18,7 @@ public function getNamespace(): string {
 		return 'version';
 	}
 	
-	public function setVersion(ResourceInterface $resource, $version) {
-		if ($resource instanceof HasExtensionMembersInterface === false) {
-			throw new InputException('resource doesn\'t have extension members');
-		}
-		
+	public function setVersion(ResourceInterface & HasExtensionMembersInterface $resource, string $version): void {
 		if ($resource instanceof ResourceDocument) {
 			$resource->getResource()->addExtensionMember($this, 'id', $version);
 		}
diff --git a/tests/example_output/at_members_everywhere/at_members_everywhere.php b/tests/example_output/at_members_everywhere/at_members_everywhere.php
index a6774a0d..49c1c29c 100644
--- a/tests/example_output/at_members_everywhere/at_members_everywhere.php
+++ b/tests/example_output/at_members_everywhere/at_members_everywhere.php
@@ -17,7 +17,7 @@
 use alsvanzelf\jsonapi\objects\ResourceObject;
 
 class at_members_everywhere {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ResourceDocument {
 		/**
 		 * root
 		 */
diff --git a/tests/example_output/at_members_in_errors/at_members_in_errors.php b/tests/example_output/at_members_in_errors/at_members_in_errors.php
index e937eb88..55783709 100644
--- a/tests/example_output/at_members_in_errors/at_members_in_errors.php
+++ b/tests/example_output/at_members_in_errors/at_members_in_errors.php
@@ -12,7 +12,7 @@
 use alsvanzelf\jsonapi\objects\MetaObject;
 
 class at_members_in_errors {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ErrorsDocument {
 		/**
 		 * root
 		 */
diff --git a/tests/example_output/collection/collection.php b/tests/example_output/collection/collection.php
index 991fbaee..a7a3e4f4 100644
--- a/tests/example_output/collection/collection.php
+++ b/tests/example_output/collection/collection.php
@@ -9,7 +9,7 @@
 use alsvanzelf\jsonapiTests\example_output\ExampleUser;
 
 class collection {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): CollectionDocument {
 		$user1        = new ExampleUser(1);
 		$user1->name  = 'Ford Prefect';
 		$user1->heads = 1;
@@ -29,7 +29,7 @@ public static function createJsonapiDocument() {
 		foreach ($users as $user) {
 			$resource = ResourceObject::fromObject($user, 'user', $user->id);
 			
-			if ($user->id == 42) {
+			if ($user->id === 42) {
 				$ship = new ResourceObject('ship', 5);
 				$ship->add('name', 'Heart of Gold');
 				$resource->addRelationship('ship', $ship);
diff --git a/tests/example_output/collection_canonical/collection_canonical.php b/tests/example_output/collection_canonical/collection_canonical.php
index a58f9451..3ea39447 100644
--- a/tests/example_output/collection_canonical/collection_canonical.php
+++ b/tests/example_output/collection_canonical/collection_canonical.php
@@ -8,7 +8,7 @@
 use alsvanzelf\jsonapi\objects\ResourceObject;
 
 class collection_canonical {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): CollectionDocument {
 		$articleRecords = [
 			1 => [
 				'title'    => 'JSON:API paints my bikeshed!',
diff --git a/tests/example_output/cursor_pagination_profile/cursor_pagination_profile.php b/tests/example_output/cursor_pagination_profile/cursor_pagination_profile.php
index 77363cdf..ccf26f69 100644
--- a/tests/example_output/cursor_pagination_profile/cursor_pagination_profile.php
+++ b/tests/example_output/cursor_pagination_profile/cursor_pagination_profile.php
@@ -9,7 +9,7 @@
 use alsvanzelf\jsonapi\profiles\CursorPaginationProfile;
 
 class cursor_pagination_profile {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): CollectionDocument {
 		$profile = new CursorPaginationProfile();
 		
 		$user1  = new ResourceObject('user', 1);
diff --git a/tests/example_output/errors_all_options/errors_all_options.php b/tests/example_output/errors_all_options/errors_all_options.php
index 6d44d3a8..fd9b3dc5 100644
--- a/tests/example_output/errors_all_options/errors_all_options.php
+++ b/tests/example_output/errors_all_options/errors_all_options.php
@@ -8,7 +8,7 @@
 use alsvanzelf\jsonapi\objects\ErrorObject;
 
 class errors_all_options {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ErrorsDocument {
 		$errorHumanApi = new ErrorObject('Invalid input', 'Too much options', 'Please, choose a bit less. Consult your ...', 'https://www.example.com/explanation.html', 'https://www.example.com/documentation.html');
 		
 		$errorSpecApi = new ErrorObject();
diff --git a/tests/example_output/errors_exception_native/errors_exception_native.php b/tests/example_output/errors_exception_native/errors_exception_native.php
index 9cc0e54d..933a4d15 100644
--- a/tests/example_output/errors_exception_native/errors_exception_native.php
+++ b/tests/example_output/errors_exception_native/errors_exception_native.php
@@ -7,7 +7,7 @@
 use alsvanzelf\jsonapi\ErrorsDocument;
 
 class errors_exception_native {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ErrorsDocument {
 		$exception = new \Exception('unknown user', 404);
 		$options = [
 			'includeExceptionTrace'    => false,
diff --git a/tests/example_output/extension/extension.php b/tests/example_output/extension/extension.php
index 8870a337..2648ebb3 100644
--- a/tests/example_output/extension/extension.php
+++ b/tests/example_output/extension/extension.php
@@ -8,7 +8,7 @@
 use alsvanzelf\jsonapiTests\example_output\ExampleVersionExtension;
 
 class extension {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ResourceDocument {
 		$extension = new ExampleVersionExtension();
 		
 		$document = new ResourceDocument('user', 42);
diff --git a/tests/example_output/extension_members_everywhere/extension_members_everywhere.php b/tests/example_output/extension_members_everywhere/extension_members_everywhere.php
index 6790a1f3..9b4779fb 100644
--- a/tests/example_output/extension_members_everywhere/extension_members_everywhere.php
+++ b/tests/example_output/extension_members_everywhere/extension_members_everywhere.php
@@ -18,7 +18,7 @@
 use alsvanzelf\jsonapiTests\example_output\ExampleEverywhereExtension;
 
 class extension_members_everywhere {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ResourceDocument {
 		$extension = new ExampleEverywhereExtension();
 		
 		$document = new ResourceDocument('user', 42);
diff --git a/tests/example_output/meta_only/meta_only.php b/tests/example_output/meta_only/meta_only.php
index 2bf360d4..2aee4e7d 100644
--- a/tests/example_output/meta_only/meta_only.php
+++ b/tests/example_output/meta_only/meta_only.php
@@ -7,7 +7,7 @@
 use alsvanzelf\jsonapi\MetaDocument;
 
 class meta_only {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): MetaDocument {
 		$document = new MetaDocument();
 		$document->addMeta('foo', 'bar');
 		
diff --git a/tests/example_output/null_values/null_values.php b/tests/example_output/null_values/null_values.php
index 488910b9..f8fd8e1e 100644
--- a/tests/example_output/null_values/null_values.php
+++ b/tests/example_output/null_values/null_values.php
@@ -10,7 +10,7 @@
 use alsvanzelf\jsonapi\objects\RelationshipObject;
 
 class null_values {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ResourceDocument {
 		$document = new ResourceDocument('user', 42);
 		
 		$document->add('foo', null);
diff --git a/tests/example_output/profile/profile.php b/tests/example_output/profile/profile.php
index 56bdde48..0796a3ac 100644
--- a/tests/example_output/profile/profile.php
+++ b/tests/example_output/profile/profile.php
@@ -8,7 +8,7 @@
 use alsvanzelf\jsonapiTests\example_output\ExampleTimestampsProfile;
 
 class profile {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ResourceDocument {
 		$profile = new ExampleTimestampsProfile();
 		
 		$document = new ResourceDocument('user', 42);
diff --git a/tests/example_output/relationship_to_many_document/relationship_to_many_document.php b/tests/example_output/relationship_to_many_document/relationship_to_many_document.php
index d5ea3561..de34adf6 100644
--- a/tests/example_output/relationship_to_many_document/relationship_to_many_document.php
+++ b/tests/example_output/relationship_to_many_document/relationship_to_many_document.php
@@ -7,7 +7,7 @@
 use alsvanzelf\jsonapi\CollectionDocument;
 
 class relationship_to_many_document {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): CollectionDocument {
 		$document = new CollectionDocument();
 		$document->add('tags', 2);
 		$document->add('tags', 3);
diff --git a/tests/example_output/relationship_to_one_document/relationship_to_one_document.php b/tests/example_output/relationship_to_one_document/relationship_to_one_document.php
index 25979b76..1d5200a8 100644
--- a/tests/example_output/relationship_to_one_document/relationship_to_one_document.php
+++ b/tests/example_output/relationship_to_one_document/relationship_to_one_document.php
@@ -8,7 +8,7 @@
 use alsvanzelf\jsonapi\enums\DocumentLevelEnum;
 
 class relationship_to_one_document {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ResourceDocument {
 		$document = new ResourceDocument('author', 12);
 		
 		$document->setSelfLink('/articles/1/relationship/author', level: DocumentLevelEnum::Root);
diff --git a/tests/example_output/relationships/relationships.php b/tests/example_output/relationships/relationships.php
index 4fc9d1ed..8b01eef3 100644
--- a/tests/example_output/relationships/relationships.php
+++ b/tests/example_output/relationships/relationships.php
@@ -11,7 +11,7 @@
 use alsvanzelf\jsonapi\objects\ResourceObject;
 
 class relationships {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ResourceDocument {
 		$document = new ResourceDocument('user', 1);
 		
 		$ship1Resource = new ResourceObject('ship', 24);
diff --git a/tests/example_output/resource_document_identifier_only/resource_document_identifier_only.php b/tests/example_output/resource_document_identifier_only/resource_document_identifier_only.php
index 3c960584..72511a9a 100644
--- a/tests/example_output/resource_document_identifier_only/resource_document_identifier_only.php
+++ b/tests/example_output/resource_document_identifier_only/resource_document_identifier_only.php
@@ -7,7 +7,7 @@
 use alsvanzelf\jsonapi\ResourceDocument;
 
 class resource_document_identifier_only {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ResourceDocument {
 		return new ResourceDocument('user', 42);
 	}
 }
diff --git a/tests/example_output/resource_human_api/resource_human_api.php b/tests/example_output/resource_human_api/resource_human_api.php
index 7f7d3284..60a3e83d 100644
--- a/tests/example_output/resource_human_api/resource_human_api.php
+++ b/tests/example_output/resource_human_api/resource_human_api.php
@@ -8,7 +8,7 @@
 use alsvanzelf\jsonapiTests\example_output\ExampleUser;
 
 class resource_human_api {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ResourceDocument {
 		$user1        = new ExampleUser(1);
 		$user1->name  = 'Ford Prefect';
 		$user1->heads = 1;
diff --git a/tests/example_output/resource_links/resource_links.php b/tests/example_output/resource_links/resource_links.php
index 8ce95ac7..48caf52e 100644
--- a/tests/example_output/resource_links/resource_links.php
+++ b/tests/example_output/resource_links/resource_links.php
@@ -9,7 +9,7 @@
 use alsvanzelf\jsonapiTests\example_output\ExampleUser;
 
 class resource_links {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ResourceDocument {
 		$user42        = new ExampleUser(42);
 		$user42->name  = 'Zaphod Beeblebrox';
 		$user42->heads = 2;
diff --git a/tests/example_output/resource_nested_relations/resource_nested_relations.php b/tests/example_output/resource_nested_relations/resource_nested_relations.php
index 244c5574..a81c99f1 100644
--- a/tests/example_output/resource_nested_relations/resource_nested_relations.php
+++ b/tests/example_output/resource_nested_relations/resource_nested_relations.php
@@ -9,7 +9,7 @@
 use alsvanzelf\jsonapiTests\example_output\ExampleUser;
 
 class resource_nested_relations {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ResourceDocument {
 		$user42        = new ExampleUser(42);
 		$user42->name  = 'Zaphod Beeblebrox';
 		$user42->heads = 2;
diff --git a/tests/example_output/resource_spec_api/resource_spec_api.php b/tests/example_output/resource_spec_api/resource_spec_api.php
index 62bcc5e6..fd542c66 100644
--- a/tests/example_output/resource_spec_api/resource_spec_api.php
+++ b/tests/example_output/resource_spec_api/resource_spec_api.php
@@ -15,7 +15,7 @@
 use alsvanzelf\jsonapiTests\example_output\ExampleUser;
 
 class resource_spec_api {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): ResourceDocument {
 		$user1        = new ExampleUser(1);
 		$user1->name  = 'Ford Prefect';
 		$user1->heads = 1;
diff --git a/tests/example_output/status_only/status_only.php b/tests/example_output/status_only/status_only.php
index 209e9cb7..e141fdbf 100644
--- a/tests/example_output/status_only/status_only.php
+++ b/tests/example_output/status_only/status_only.php
@@ -7,7 +7,7 @@
 use alsvanzelf\jsonapi\MetaDocument;
 
 class status_only {
-	public static function createJsonapiDocument() {
+	public static function createJsonapiDocument(): MetaDocument {
 		$document = new MetaDocument();
 		$document->setHttpStatusCode(201);
 		
diff --git a/tests/extensions/AtomicOperationsDocumentTest.php b/tests/extensions/AtomicOperationsDocumentTest.php
index 56b9bb9c..af9bee67 100644
--- a/tests/extensions/AtomicOperationsDocumentTest.php
+++ b/tests/extensions/AtomicOperationsDocumentTest.php
@@ -7,12 +7,11 @@
 use alsvanzelf\jsonapi\extensions\AtomicOperationsDocument;
 use alsvanzelf\jsonapi\extensions\AtomicOperationsExtension;
 use alsvanzelf\jsonapi\objects\ResourceObject;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-/**
- * @group Extensions
- */
-class AtomicOperationsDocumentTest extends TestCase {
+#[Group('Extensions')]
+final class AtomicOperationsDocumentTest extends TestCase {
 	public function testSetResults_HappyPath(): void {
 		$document = new AtomicOperationsDocument();
 		
diff --git a/tests/helpers/AtMemberManagerTest.php b/tests/helpers/AtMemberManagerTest.php
index 40174cc9..49656536 100644
--- a/tests/helpers/AtMemberManagerTest.php
+++ b/tests/helpers/AtMemberManagerTest.php
@@ -8,7 +8,7 @@
 use alsvanzelf\jsonapi\helpers\AtMemberManager;
 use PHPUnit\Framework\TestCase;
 
-class AtMemberManagerTest extends TestCase {
+final class AtMemberManagerTest extends TestCase {
 	private static object $helper;
 	
 	public static function setUpBeforeClass(): void {
diff --git a/tests/helpers/ExtensionMemberManagerTest.php b/tests/helpers/ExtensionMemberManagerTest.php
index deee7e32..e9bd1ae7 100644
--- a/tests/helpers/ExtensionMemberManagerTest.php
+++ b/tests/helpers/ExtensionMemberManagerTest.php
@@ -7,12 +7,11 @@
 use alsvanzelf\jsonapi\exceptions\InputException;
 use alsvanzelf\jsonapi\helpers\ExtensionMemberManager;
 use alsvanzelf\jsonapi\interfaces\ExtensionInterface;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-/**
- * @group Extensions
- */
-class ExtensionMemberManagerTest extends TestCase {
+#[Group('Extensions')]
+final class ExtensionMemberManagerTest extends TestCase {
 	private static object $helper;
 	
 	public static function setUpBeforeClass(): void {
diff --git a/tests/helpers/HttpStatusCodeManagerTest.php b/tests/helpers/HttpStatusCodeManagerTest.php
index 9fe2b96f..c30abc1f 100644
--- a/tests/helpers/HttpStatusCodeManagerTest.php
+++ b/tests/helpers/HttpStatusCodeManagerTest.php
@@ -8,7 +8,7 @@
 use alsvanzelf\jsonapi\helpers\HttpStatusCodeManager;
 use PHPUnit\Framework\TestCase;
 
-class HttpStatusCodeManagerTest extends TestCase {
+final class HttpStatusCodeManagerTest extends TestCase {
 	private static object $helper;
 	
 	public static function setUpBeforeClass(): void {
diff --git a/tests/helpers/LinksManagerTest.php b/tests/helpers/LinksManagerTest.php
index 47df373c..836099fc 100644
--- a/tests/helpers/LinksManagerTest.php
+++ b/tests/helpers/LinksManagerTest.php
@@ -8,10 +8,10 @@
 use alsvanzelf\jsonapi\objects\LinkObject;
 use PHPUnit\Framework\TestCase;
 
-class LinksManagerTest extends TestCase {
+final class LinksManagerTest extends TestCase {
 	private object $linksManager;
 	
-	public function setUp(): void {
+	protected function setUp(): void {
 		// using LinksManager to make it non-trait to test against it
 		$this->linksManager = new class {
 			use LinksManager;
@@ -20,7 +20,7 @@ public function setUp(): void {
 			 * @return array<string, string|array{href: string}>
 			 */
 			public function toArray(): array {
-				return $this->links->toArray();
+				return $this->links->toArray(); // @phpstan-ignore return.type (toArray() methods don't have explicit array shapes yet)
 			}
 		};
 	}
diff --git a/tests/helpers/RequestParserTest.php b/tests/helpers/RequestParserTest.php
index 2f03689c..9bfd5ab2 100644
--- a/tests/helpers/RequestParserTest.php
+++ b/tests/helpers/RequestParserTest.php
@@ -13,7 +13,7 @@
 use Psr\Http\Message\StreamInterface;
 use Psr\Http\Message\UriInterface;
 
-class RequestParserTest extends TestCase {
+final class RequestParserTest extends TestCase {
 	public function testFromSuperglobals_HappyPath(): void {
 		$_GET = [
 			'include' => 'ship,ship.wing',
@@ -87,12 +87,9 @@ public function testFromSuperglobals_WithPhpInputStream(): void {
 		$_SERVER['REQUEST_URI']    = '/';
 		$_SERVER['CONTENT_TYPE']   = ContentTypeEnum::Official->value;
 		
+		// empty $_POST so we get a bit more test coverage for input stream processing
 		$_GET  = [];
-		$_POST = [
-			'meta' => [
-				'foo' => 'bar',
-			],
-		];
+		$_POST = [];
 		
 		$requestParser = RequestParser::fromSuperglobals();
 		
@@ -188,10 +185,6 @@ public function testFromPsrRequest_WithRequestInterface(): void {
 	}
 	
 	public function testFromPsrRequest_WithEmptyDocument(): void {
-		$selfLink        = '';
-		$queryParameters = [];
-		$document        = null;
-		
 		$request = parent::createConfiguredStub(RequestInterface::class, [
 			'getBody' => parent::createConfiguredStub(StreamInterface::class, ['getContents' => '']),
 			'getUri'  => parent::createConfiguredStub(UriInterface::class, ['getQuery'   => '']),
diff --git a/tests/objects/AttributesObjectTest.php b/tests/objects/AttributesObjectTest.php
index ca604990..061c174b 100644
--- a/tests/objects/AttributesObjectTest.php
+++ b/tests/objects/AttributesObjectTest.php
@@ -6,9 +6,10 @@
 
 use alsvanzelf\jsonapi\interfaces\ExtensionInterface;
 use alsvanzelf\jsonapi\objects\AttributesObject;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-class AttributesObjectTest extends TestCase {
+final class AttributesObjectTest extends TestCase {
 	public function testFromObject_HappyPath(): void {
 		$object = new \stdClass();
 		$object->foo = 'bar';
@@ -67,9 +68,7 @@ public function testAdd_WithObject(): void {
 		parent::assertSame('baz', $array['foo']['bar']);
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testAddExtensionMember_HappyPath(): void {
 		$attributesObject = new AttributesObject();
 		$extension        = parent::createConfiguredStub(ExtensionInterface::class, ['getNamespace' => 'test']);
diff --git a/tests/objects/ErrorObjectTest.php b/tests/objects/ErrorObjectTest.php
index 8bb42453..ba374c79 100644
--- a/tests/objects/ErrorObjectTest.php
+++ b/tests/objects/ErrorObjectTest.php
@@ -7,9 +7,10 @@
 use alsvanzelf\jsonapi\exceptions\InputException;
 use alsvanzelf\jsonapi\interfaces\ExtensionInterface;
 use alsvanzelf\jsonapi\objects\ErrorObject;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-class ErrorObjectTest extends TestCase {
+final class ErrorObjectTest extends TestCase {
 	public function testFromException_HappyPath(): void {
 		$exception    = new \Exception('foo', 1);
 		$expectedLine = (__LINE__ - 1);
@@ -42,7 +43,6 @@ public function testFromException_HappyPath(): void {
 	
 	public function testFromException_DoNotExposeTrace(): void {
 		$exception    = new \Exception('foo', 1);
-		$expectedLine = (__LINE__ - 1);
 		$options      = ['includeExceptionTrace' => false];
 		$errorObject  = ErrorObject::fromException($exception, $options);
 		
@@ -155,9 +155,7 @@ public function testIsEmpty_All(): void {
 		parent::assertFalse($errorObject->isEmpty());
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testToArray_WithExtensionMembers(): void {
 		$errorObject = new ErrorObject();
 		$extension   = parent::createConfiguredStub(ExtensionInterface::class, ['getNamespace' => 'test']);
diff --git a/tests/objects/JsonapiObjectTest.php b/tests/objects/JsonapiObjectTest.php
index 29965b54..2ba8a776 100644
--- a/tests/objects/JsonapiObjectTest.php
+++ b/tests/objects/JsonapiObjectTest.php
@@ -7,9 +7,10 @@
 use alsvanzelf\jsonapi\interfaces\ExtensionInterface;
 use alsvanzelf\jsonapi\interfaces\ProfileInterface;
 use alsvanzelf\jsonapi\objects\JsonapiObject;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-class JsonapiObjectTest extends TestCase {
+final class JsonapiObjectTest extends TestCase {
 	public function testAddMeta_HappyPath(): void {
 		$jsonapiObject = new JsonapiObject($version=null);
 		
@@ -36,9 +37,7 @@ public function testIsEmpty_WithAtMembers(): void {
 		parent::assertFalse($jsonapiObject->isEmpty());
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testIsEmpty_WithExtensionLink(): void {
 		$jsonapiObject = new JsonapiObject($version=null);
 		
@@ -49,9 +48,7 @@ public function testIsEmpty_WithExtensionLink(): void {
 		parent::assertFalse($jsonapiObject->isEmpty());
 	}
 	
-	/**
-	 * @group Profiles
-	 */
+	#[Group('Profiles')]
 	public function testIsEmpty_WithProfileLink(): void {
 		$jsonapiObject = new JsonapiObject($version=null);
 		
@@ -62,9 +59,7 @@ public function testIsEmpty_WithProfileLink(): void {
 		parent::assertFalse($jsonapiObject->isEmpty());
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testIsEmpty_WithExtensionMembers(): void {
 		$jsonapiObject = new JsonapiObject($version=null);
 		
diff --git a/tests/objects/LinkObjectTest.php b/tests/objects/LinkObjectTest.php
index fe6da28a..78b5eab2 100644
--- a/tests/objects/LinkObjectTest.php
+++ b/tests/objects/LinkObjectTest.php
@@ -6,9 +6,10 @@
 
 use alsvanzelf\jsonapi\interfaces\ExtensionInterface;
 use alsvanzelf\jsonapi\objects\LinkObject;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-class LinkObjectTest extends TestCase {
+final class LinkObjectTest extends TestCase {
 	public function testSetDescribedBy_HappyPath(): void {
 		$linkObject = new LinkObject();
 		
@@ -155,9 +156,7 @@ public function testIsEmpty_WithAtMembers(): void {
 		parent::assertFalse($linkObject->isEmpty());
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testIsEmpty_WithExtensionMembers(): void {
 		$linkObject = new LinkObject();
 		
diff --git a/tests/objects/LinksObjectTest.php b/tests/objects/LinksObjectTest.php
index 846766ed..ff38232e 100644
--- a/tests/objects/LinksObjectTest.php
+++ b/tests/objects/LinksObjectTest.php
@@ -10,7 +10,7 @@
 use alsvanzelf\jsonapi\objects\LinksObject;
 use PHPUnit\Framework\TestCase;
 
-class LinksObjectTest extends TestCase {
+final class LinksObjectTest extends TestCase {
 	public function testFromObject_HappyPath(): void {
 		$object = new \stdClass();
 		$object->foo = 'https://jsonapi.org';
diff --git a/tests/objects/MetaObjectTest.php b/tests/objects/MetaObjectTest.php
index baf46664..050254f1 100644
--- a/tests/objects/MetaObjectTest.php
+++ b/tests/objects/MetaObjectTest.php
@@ -6,9 +6,10 @@
 
 use alsvanzelf\jsonapi\interfaces\ExtensionInterface;
 use alsvanzelf\jsonapi\objects\MetaObject;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-class MetaObjectTest extends TestCase {
+final class MetaObjectTest extends TestCase {
 	public function testAdd_AllowsMixedValue(): void {
 		$metaObject = new MetaObject();
 		$metaObject->add('array-list', ['foo']);
@@ -49,9 +50,7 @@ public function testIsEmpty_WithAtMembers(): void {
 		parent::assertFalse($metaObject->isEmpty());
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testIsEmpty_WithExtensionMembers(): void {
 		$metaObject = new MetaObject();
 		
diff --git a/tests/objects/RelationshipObjectTest.php b/tests/objects/RelationshipObjectTest.php
index e35a0a51..174e83f8 100644
--- a/tests/objects/RelationshipObjectTest.php
+++ b/tests/objects/RelationshipObjectTest.php
@@ -13,9 +13,10 @@
 use alsvanzelf\jsonapi\objects\RelationshipObject;
 use alsvanzelf\jsonapi\objects\ResourceIdentifierObject;
 use alsvanzelf\jsonapi\objects\ResourceObject;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-class RelationshipObjectTest extends TestCase {
+final class RelationshipObjectTest extends TestCase {
 	public function testConstructor_ToOne(): void {
 		$relationshipObject = new RelationshipObject(RelationshipTypeEnum::ToOne);
 		$relationshipObject->setResource(new ResourceObject('user', 42));
@@ -298,9 +299,7 @@ public function testIsEmpty_WithAtMembers(): void {
 		parent::assertFalse($relationshipObject->isEmpty());
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testIsEmpty_WithExtensionMembers(): void {
 		$relationshipObject = new RelationshipObject(RelationshipTypeEnum::ToOne);
 		
@@ -311,7 +310,10 @@ public function testIsEmpty_WithExtensionMembers(): void {
 		parent::assertFalse($relationshipObject->isEmpty());
 	}
 	
-	private function validateToOneRelationshipArray(array $array) {
+	/**
+	 * @param array<string, mixed> $array
+	 */
+	private function validateToOneRelationshipArray(array $array): void {
 		parent::assertNotEmpty($array);
 		parent::assertArrayHasKey('data', $array);
 		parent::assertArrayHasKey('type', $array['data']);
@@ -320,7 +322,10 @@ private function validateToOneRelationshipArray(array $array) {
 		parent::assertSame('42', $array['data']['id']);
 	}
 	
-	private function validateToManyRelationshipArray(array $array) {
+	/**
+	 * @param array<string, mixed> $array
+	 */
+	private function validateToManyRelationshipArray(array $array): void {
 		parent::assertNotEmpty($array);
 		parent::assertArrayHasKey('data', $array);
 		parent::assertCount(1, $array['data']);
diff --git a/tests/objects/RelationshipsObjectTest.php b/tests/objects/RelationshipsObjectTest.php
index 6b7f0af3..a345b1a1 100644
--- a/tests/objects/RelationshipsObjectTest.php
+++ b/tests/objects/RelationshipsObjectTest.php
@@ -12,7 +12,7 @@
 use alsvanzelf\jsonapi\objects\ResourceObject;
 use PHPUnit\Framework\TestCase;
 
-class RelationshipsObjectTest extends TestCase {
+final class RelationshipsObjectTest extends TestCase {
 	public function testAdd_HappyPath(): void {
 		$relationshipsObject = new RelationshipsObject();
 		$relationshipsObject->add('foo', new ResourceObject('user', 42));
diff --git a/tests/objects/ResourceIdentifierObjectTest.php b/tests/objects/ResourceIdentifierObjectTest.php
index 64e65ff2..e1035347 100644
--- a/tests/objects/ResourceIdentifierObjectTest.php
+++ b/tests/objects/ResourceIdentifierObjectTest.php
@@ -6,11 +6,14 @@
 
 use alsvanzelf\jsonapi\exceptions\DuplicateException;
 use alsvanzelf\jsonapi\exceptions\Exception;
+use alsvanzelf\jsonapi\exceptions\InputException;
 use alsvanzelf\jsonapi\interfaces\ExtensionInterface;
 use alsvanzelf\jsonapi\objects\ResourceIdentifierObject;
+use alsvanzelf\jsonapi\objects\ResourceObject;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-class ResourceIdentifierObjectTest extends TestCase {
+final class ResourceIdentifierObjectTest extends TestCase {
 	public function testSetId_HappyPath(): void {
 		$resourceIdentifierObject = new ResourceIdentifierObject();
 		$resourceIdentifierObject->setType('test');
@@ -55,6 +58,35 @@ public function testSetLocalId_WithIdAlreadySet(): void {
 		$resourceIdentifierObject->setLocalId('uuid-1');
 	}
 	
+	public function testFromResourceObject_HappyPath(): void {
+		$resource = new ResourceObject('test', 1);
+		$resource->addAttribute('foo', 'bar');
+		
+		$array = $resource->toArray();
+		
+		parent::assertSame('test', $array['type']);
+		parent::assertSame('1', $array['id']);
+		parent::assertArrayHasKey('attributes', $array);
+		
+		$resourceIdentifierObject = ResourceIdentifierObject::fromResourceObject($resource);
+		
+		$array = $resourceIdentifierObject->toArray();
+		
+		parent::assertSame('test', $array['type']);
+		parent::assertSame('1', $array['id']);
+		parent::assertArrayNotHasKey('attributes', $array);
+	}
+	
+	public function testFromResourceObject_NoFullIdentification(): void {
+		$resource = new ResourceObject();
+		$resource->toArray();
+		
+		$this->expectException(InputException::class);
+		$this->expectExceptionMessage('resource has no identification yet');
+		
+		ResourceIdentifierObject::fromResourceObject($resource);
+	}
+	
 	public function testEquals_HappyPath(): void {
 		$one = new ResourceIdentifierObject('test', 1);
 		$two = new ResourceIdentifierObject('test', 2);
@@ -168,6 +200,13 @@ public function testGetIdentificationKey_NoFullIdentification(): void {
 		$resourceIdentifierObject->getIdentificationKey();
 	}
 	
+	public function testIsEmpty_IdWithoutType(): void {
+		$resourceIdentifierObject = new ResourceIdentifierObject();
+		$resourceIdentifierObject->setId(42);
+		
+		parent::assertFalse($resourceIdentifierObject->isEmpty());
+	}
+	
 	public function testIsEmpty_WithAtMembers(): void {
 		$resourceIdentifierObject = new ResourceIdentifierObject();
 		
@@ -178,9 +217,7 @@ public function testIsEmpty_WithAtMembers(): void {
 		parent::assertFalse($resourceIdentifierObject->isEmpty());
 	}
 	
-	/**
-	 * @group Extensions
-	 */
+	#[Group('Extensions')]
 	public function testIsEmpty_WithExtensionMembers(): void {
 		$resourceIdentifierObject = new ResourceIdentifierObject();
 		
@@ -190,4 +227,14 @@ public function testIsEmpty_WithExtensionMembers(): void {
 		
 		parent::assertFalse($resourceIdentifierObject->isEmpty());
 	}
+	
+	public function testPrimaryId_NoFullIdentification(): void {
+		$resourceIdentifierObject = new ResourceIdentifierObject();
+		$primaryIdMethod = new \ReflectionMethod($resourceIdentifierObject, 'primaryId');
+		
+		$this->expectException(Exception::class);
+		$this->expectExceptionMessage('resource has no identification yet');
+		
+		$primaryIdMethod->invoke($resourceIdentifierObject);
+	}
 }
diff --git a/tests/objects/ResourceObjectTest.php b/tests/objects/ResourceObjectTest.php
index 0b1410f9..1699fd2c 100644
--- a/tests/objects/ResourceObjectTest.php
+++ b/tests/objects/ResourceObjectTest.php
@@ -14,7 +14,7 @@
 use alsvanzelf\jsonapi\objects\ResourceObject;
 use PHPUnit\Framework\TestCase;
 
-class ResourceObjectTest extends TestCase {
+final class ResourceObjectTest extends TestCase {
 	public function testConstructor_ClientDocumentWithoutId(): void {
 		$resourceObject = new ResourceObject('user');
 		$resourceObject->add('foo', 'bar');
diff --git a/tests/profiles/CursorPaginationProfileTest.php b/tests/profiles/CursorPaginationProfileTest.php
index 42250a6d..9df411a3 100644
--- a/tests/profiles/CursorPaginationProfileTest.php
+++ b/tests/profiles/CursorPaginationProfileTest.php
@@ -6,15 +6,15 @@
 
 use alsvanzelf\jsonapi\CollectionDocument;
 use alsvanzelf\jsonapi\ResourceDocument;
+use alsvanzelf\jsonapi\exceptions\InputException;
 use alsvanzelf\jsonapi\objects\RelationshipObject;
 use alsvanzelf\jsonapi\objects\ResourceObject;
 use alsvanzelf\jsonapi\profiles\CursorPaginationProfile;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\TestCase;
 
-/**
- * @group Profiles
- */
-class CursorPaginationProfileTest extends TestCase {
+#[Group('Profiles')]
+final class CursorPaginationProfileTest extends TestCase {
 	public function testSetLinks_HappyPath(): void {
 		$profile          = new CursorPaginationProfile();
 		$collection       = new CollectionDocument();
@@ -76,21 +76,30 @@ public function test_WithRelationship(): void {
 		parent::assertArrayHasKey('data', $array);
 		parent::assertArrayHasKey('relationships', $array['data']);
 		parent::assertArrayHasKey('people', $array['data']['relationships']);
-		parent::assertArrayHasKey('links', $array['data']['relationships']['people']);
-		parent::assertArrayHasKey('data', $array['data']['relationships']['people']);
-		parent::assertArrayHasKey('meta', $array['data']['relationships']['people']);
-		parent::assertArrayHasKey('prev', $array['data']['relationships']['people']['links']);
-		parent::assertArrayHasKey('next', $array['data']['relationships']['people']['links']);
-		parent::assertArrayHasKey('page', $array['data']['relationships']['people']['meta']);
-		parent::assertArrayHasKey('href', $array['data']['relationships']['people']['links']['prev']);
-		parent::assertArrayHasKey('href', $array['data']['relationships']['people']['links']['next']);
-		parent::assertArrayHasKey('total', $array['data']['relationships']['people']['meta']['page']);
-		parent::assertArrayHasKey('estimatedTotal', $array['data']['relationships']['people']['meta']['page']);
-		parent::assertArrayHasKey('bestGuess', $array['data']['relationships']['people']['meta']['page']['estimatedTotal']);
-		parent::assertCount(3, $array['data']['relationships']['people']['data']);
-		parent::assertArrayHasKey('meta', $array['data']['relationships']['people']['data'][0]);
-		parent::assertArrayHasKey('page', $array['data']['relationships']['people']['data'][0]['meta']);
-		parent::assertArrayHasKey('cursor', $array['data']['relationships']['people']['data'][0]['meta']['page']);
+		
+		// re-map nested arrays to variables to speed up phpstan
+		// without it, this file takes 10 seconds (!) more to process
+		
+		$people = $array['data']['relationships']['people'];
+		parent::assertArrayHasKey('links', $people);
+		parent::assertArrayHasKey('data', $people);
+		parent::assertArrayHasKey('meta', $people);
+		parent::assertArrayHasKey('prev', $people['links']);
+		parent::assertArrayHasKey('next', $people['links']);
+		parent::assertArrayHasKey('page', $people['meta']);
+		parent::assertArrayHasKey('href', $people['links']['prev']);
+		parent::assertArrayHasKey('href', $people['links']['next']);
+		
+		$peopleMeta = $people['meta'];
+		parent::assertArrayHasKey('total', $peopleMeta['page']);
+		parent::assertArrayHasKey('estimatedTotal', $peopleMeta['page']);
+		parent::assertArrayHasKey('bestGuess', $peopleMeta['page']['estimatedTotal']);
+		parent::assertCount(3, $people['data']);
+		
+		$firstPerson = $people['data'][0];
+		parent::assertArrayHasKey('meta', $firstPerson);
+		parent::assertArrayHasKey('page', $firstPerson['meta']);
+		parent::assertArrayHasKey('cursor', $firstPerson['meta']['page']);
 	}
 	
 	public function testSetLinksFirstPage_HappyPath(): void {
@@ -343,4 +352,18 @@ public function testSetQueryParameter_EncodedUrl(): void {
 		
 		parent::assertSame('/people?sort=x&page%5Bsize%5D=10&page%5Bafter%5D=bar', $newUrl);
 	}
+	
+	public function testSetQueryParameter_WithBrokenUrl(): void {
+		$profile = new CursorPaginationProfile();
+		$method  = new \ReflectionMethod($profile, 'setQueryParameter');
+		
+		$url   = 'foo';
+		$key   = 'page[after]';
+		$value = 'bar';
+		
+		$this->expectException(InputException::class);
+		$this->expectExceptionMessage('missing or broken query parameters in url');
+		
+		$method->invoke($profile, $url, $key, $value);
+	}
 }