diff --git a/.phpstan.neon b/.phpstan.neon
index 5567202..5199950 100644
--- a/.phpstan.neon
+++ b/.phpstan.neon
@@ -76,3 +76,15 @@ parameters:
 			count: 1
 			path: tests/Unit/V1/ResourceNullTest.php
 			# We are providing an invalid parameter to test the deprecation message
+
+		-
+			message: "#^Parameter \\#1 \\$key of method Art4\\\\JsonApiClient\\\\Tests\\\\Fixtures\\\\AccessableTraitMock\\:\\:get\\(\\) expects Art4\\\\JsonApiClient\\\\Helper\\\\AccessKey\\|int\\|string, mixed given\\.$#"
+			count: 1
+			path: tests/Unit/Helper/AccessableTraitTest.php
+			# We are providing an invalid parameter to test the deprecation message
+
+		-
+			message: "#^Parameter \\#1 \\$key of method Art4\\\\JsonApiClient\\\\Tests\\\\Fixtures\\\\AccessableTraitMock\\:\\:has\\(\\) expects Art4\\\\JsonApiClient\\\\Helper\\\\AccessKey\\|int\\|string, mixed given\\.$#"
+			count: 1
+			path: tests/Unit/Helper/AccessableTraitTest.php
+			# We are providing an invalid parameter to test the deprecation message
diff --git a/CHANGELOG.md b/CHANGELOG.md
index fae9c7d..30cab1d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 - Add support for PHP 8.2
 
+### Deprecated
+
+- Providing Argument #1 ($key) in `\Art4\JsonApiClient\Accessable::has()` not as `int|string` is deprecated and will throw an Exception in 2.0.0.
+- Providing Argument #1 ($key) in `\Art4\JsonApiClient\Accessable::get()` not as `int|string` is deprecated and will throw an Exception in 2.0.0.
+
 ## [1.1.0 - 2021-10-05](https://github.com/Art4/json-api-client/compare/1.0.0...1.1.0)
 
 ### Added
@@ -25,16 +30,16 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Deprecated
 
-- `\Art4\JsonApiClient\Accessable::has()` will add `bool` as a native return type declaration in v2.0, do the same in your implementation now to avoid errors.
-- `\Art4\JsonApiClient\Accessable::getKeys()` will add `array` as a native return type declaration in v2.0, do the same in your implementation now to avoid errors.
-- `\Art4\JsonApiClient\Exception\Exception` will extend `\Throwable` in v2.0, do the same in your implementation now to avoid errors.
-- `\Art4\JsonApiClient\Factory::make()` methods first parameter signature will be `string` in v2.0.
-- `\Art4\JsonApiClient\Factory::make()` will add `\Art4\JsonApiClient\Accessable` as a native return type declaration in v2.0, do the same in your implementation now to avoid errors.
-- `\Art4\JsonApiClient\Input\Input::getAsObject()` will add `\stdClass` as a native return type declaration in v2.0, do the same in your implementation now to avoid errors.
-- `\Art4\JsonApiClient\Manager::parse()` will add `\Art4\JsonApiClient\Accessable` as a native return type declaration in v2.0, do the same in your implementation now to avoid errors.
-- `\Art4\JsonApiClient\Manager::getFactory()` will add `\Art4\JsonApiClient\Factory` as a native return type declaration in v2.0, do the same in your implementation now to avoid errors.
-- `\Art4\JsonApiClient\Manager::getParam()` methods first parameter signature will be `string` in v2.0.
-- `\Art4\JsonApiClient\Serializer\Serializer::serialize()` will add `?array` as a native return type declaration in v2.0, do the same in your implementation now to avoid errors.
+- `\Art4\JsonApiClient\Accessable::has()` will add `bool` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
+- `\Art4\JsonApiClient\Accessable::getKeys()` will add `array` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
+- `\Art4\JsonApiClient\Exception\Exception` will extend `\Throwable` in 2.0.0, do the same in your implementation now to avoid errors.
+- `\Art4\JsonApiClient\Factory::make()` methods first parameter signature will be `string` in 2.0.0.
+- `\Art4\JsonApiClient\Factory::make()` will add `\Art4\JsonApiClient\Accessable` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
+- `\Art4\JsonApiClient\Input\Input::getAsObject()` will add `\stdClass` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
+- `\Art4\JsonApiClient\Manager::parse()` will add `\Art4\JsonApiClient\Accessable` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
+- `\Art4\JsonApiClient\Manager::getFactory()` will add `\Art4\JsonApiClient\Factory` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
+- `\Art4\JsonApiClient\Manager::getParam()` methods first parameter signature will be `string` in 2.0.0.
+- `\Art4\JsonApiClient\Serializer\Serializer::serialize()` will add `?array` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
 
 ## [1.0.0 - 2021-03-05](https://github.com/Art4/json-api-client/compare/0.10.2...1.0.0)
 
diff --git a/src/Accessable.php b/src/Accessable.php
index cf63145..11f3c93 100644
--- a/src/Accessable.php
+++ b/src/Accessable.php
@@ -27,22 +27,20 @@ public function get($key);
     /**
      * Check if a value exists
      *
-     * @deprecated `\Art4\JsonApiClient\Accessable::has()` will add `bool` as a native return type declaration in v2.0. Do the same in your implementation now to avoid errors.
+     * @return-type-will-change bool `\Art4\JsonApiClient\Accessable::has()` will add `bool` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
      *
      * @param mixed $key The key
      *
      * @return bool
      */
-    public function has($key);
-    // public function has($key): bool;
+    public function has($key)/*: bool */;
 
     /**
      * Returns the keys of all setted values
      *
-     * @deprecated `\Art4\JsonApiClient\Accessable::getKeys()` will add `array` as a native return type declaration in v2.0. Do the same in your implementation now to avoid errors.
+     * @return-type-will-change array `\Art4\JsonApiClient\Accessable::getKeys()` will add `array` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
      *
      * @return array<string|int> Keys of all setted values
      */
-    public function getKeys();
-    // public function getKeys(): array;
+    public function getKeys()/*: array */;
 }
diff --git a/src/Exception/AccessException.php b/src/Exception/AccessException.php
index 9edf22e..ee57d2e 100644
--- a/src/Exception/AccessException.php
+++ b/src/Exception/AccessException.php
@@ -8,4 +8,4 @@
 
 namespace Art4\JsonApiClient\Exception;
 
-class AccessException extends \RuntimeException implements Exception, \Throwable {}
+class AccessException extends \RuntimeException implements Exception {}
diff --git a/src/Exception/Exception.php b/src/Exception/Exception.php
index 0e88f54..ffdeb7c 100644
--- a/src/Exception/Exception.php
+++ b/src/Exception/Exception.php
@@ -9,7 +9,7 @@
 namespace Art4\JsonApiClient\Exception;
 
 /**
- * @deprecated `\Art4\JsonApiClient\Exception\Exception` will extend `\Throwable` in v2.0. Do the same in your implementation now to avoid errors.
+ * Please note: `\Art4\JsonApiClient\Exception\Exception` will extend `\Throwable` in 2.0.0, do the same in your implementation now to avoid errors.
  */
-// interface Exception extends \Throwable
-interface Exception {}
+interface Exception /*extends \Throwable */
+{}
diff --git a/src/Exception/FactoryException.php b/src/Exception/FactoryException.php
index 3b8ffbb..be7cb9c 100644
--- a/src/Exception/FactoryException.php
+++ b/src/Exception/FactoryException.php
@@ -8,4 +8,4 @@
 
 namespace Art4\JsonApiClient\Exception;
 
-class FactoryException extends \Exception implements Exception, \Throwable {}
+class FactoryException extends \Exception implements Exception {}
diff --git a/src/Exception/InputException.php b/src/Exception/InputException.php
index b59fe12..5ec8cc6 100644
--- a/src/Exception/InputException.php
+++ b/src/Exception/InputException.php
@@ -8,4 +8,4 @@
 
 namespace Art4\JsonApiClient\Exception;
 
-class InputException extends \Exception implements Exception, \Throwable {}
+class InputException extends \Exception implements Exception {}
diff --git a/src/Exception/ValidationException.php b/src/Exception/ValidationException.php
index 771e20a..4273774 100644
--- a/src/Exception/ValidationException.php
+++ b/src/Exception/ValidationException.php
@@ -8,4 +8,4 @@
 
 namespace Art4\JsonApiClient\Exception;
 
-class ValidationException extends \InvalidArgumentException implements Exception, \Throwable {}
+class ValidationException extends \InvalidArgumentException implements Exception {}
diff --git a/src/Factory.php b/src/Factory.php
index 7dd1ed9..d25a5c1 100644
--- a/src/Factory.php
+++ b/src/Factory.php
@@ -16,14 +16,11 @@ interface Factory
     /**
      * Create a new instance of a class
      *
-     * @deprecated The `\Art4\JsonApiClient\Factory::make()` methods first parameter signature will be `string` in v2.0.
-     * @deprecated `\Art4\JsonApiClient\Factory::make()` will add `\Art4\JsonApiClient\Accessable` as a native return type declaration in v2.0. Do the same in your implementation now to avoid errors.
+     * @return-type-will-change Accessable `\Art4\JsonApiClient\Factory::make()` will add `\Art4\JsonApiClient\Accessable` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
      *
-     * @param string $name
-     * @param array<mixed|Manager|Accessable>  $args
+     * @param array<mixed|Manager|Accessable> $args
      *
      * @return \Art4\JsonApiClient\Accessable
      */
-    public function make($name, array $args = []);
-    // public function make(string $name, array $args = []): Accessable;
+    public function make(string $name, array $args = [])/*: Accessable */;
 }
diff --git a/src/Helper/AccessKey.php b/src/Helper/AccessKey.php
index bed0120..fbc7a31 100644
--- a/src/Helper/AccessKey.php
+++ b/src/Helper/AccessKey.php
@@ -22,31 +22,20 @@ final class AccessKey extends SplStack
     /**
      * Transforms the Key to a string
      *
-     * @param int|string $key
-     *
      * @return AccessKey<string>
      */
-    public static function create($key): AccessKey
+    public static function create(string $key): AccessKey
     {
-        // Ignore arrays and objects
-        if (is_object($key) or is_array($key)) {
-            $key = '';
-        }
-
-        $key_string = strval($key);
-
-        $key = new self();
-        $key->raw = $key_string;
-
-        $keys = explode('.', $key_string);
+        $accessKey = new self();
+        $accessKey->raw = $key;
 
-        foreach ($keys as $value) {
-            $key->push($value);
+        foreach (explode('.', $key) as $value) {
+            $accessKey->push($value);
         }
 
-        $key->rewind();
+        $accessKey->rewind();
 
-        return $key;
+        return $accessKey;
     }
 
     /**
diff --git a/src/Helper/AccessableTrait.php b/src/Helper/AccessableTrait.php
index 6cee963..4a6a6ce 100644
--- a/src/Helper/AccessableTrait.php
+++ b/src/Helper/AccessableTrait.php
@@ -57,11 +57,12 @@ final public function has($key): bool
     {
         if (! is_int($key) && ! is_string($key) && (! is_object($key) || ! $key instanceof AccessKey)) {
             trigger_error(sprintf(
-                '%s::has(): Providing Argument #1 ($key) as %s is deprecated since 1.2.0, please provide as int|string|%s instead.',
+                '%s::has(): Providing Argument #1 ($key) as `%s` is deprecated since 1.2.0, please provide as `int|string` instead.',
                 get_class($this),
-                gettype($key),
-                AccessKey::class
+                gettype($key)
             ), \E_USER_DEPRECATED);
+
+            $key = '';
         }
 
         $key = $this->parseKey($key);
@@ -97,6 +98,16 @@ final public function has($key): bool
      */
     public function get($key)
     {
+        if (! is_int($key) && ! is_string($key) && (! is_object($key) || ! $key instanceof AccessKey)) {
+            trigger_error(sprintf(
+                '%s::get(): Providing Argument #1 ($key) as `%s` is deprecated since 1.2.0, please provide as `int|string` instead.',
+                get_class($this),
+                gettype($key)
+            ), \E_USER_DEPRECATED);
+
+            $key = '';
+        }
+
         $key = $this->parseKey($key);
 
         $string = $key->shift();
@@ -136,8 +147,6 @@ private function getValue(string $key)
      * Parse a dot.notated.key to an object
      *
      * @param int|string|AccessKey<string> $key The key
-     *
-     * @return AccessKey<string> The parsed key
      */
     private function parseKey($key): AccessKey
     {
@@ -145,8 +154,6 @@ private function parseKey($key): AccessKey
             return $key;
         }
 
-        $key = AccessKey::create($key);
-
-        return $key;
+        return AccessKey::create(strval($key));
     }
 }
diff --git a/src/Helper/RootAccessable.php b/src/Helper/RootAccessable.php
index 78c46ba..2983ed9 100644
--- a/src/Helper/RootAccessable.php
+++ b/src/Helper/RootAccessable.php
@@ -9,8 +9,6 @@
 namespace Art4\JsonApiClient\Helper;
 
 use Art4\JsonApiClient\Accessable;
-use Art4\JsonApiClient\Element;
-use Art4\JsonApiClient\Manager;
 
 /**
  * RootAccessable
diff --git a/src/Input/Input.php b/src/Input/Input.php
index 457a534..bb168c4 100644
--- a/src/Input/Input.php
+++ b/src/Input/Input.php
@@ -16,7 +16,7 @@ interface Input
     /**
      * Get the input as simple object
      *
-     * @deprecated `\Art4\JsonApiClient\Input\Input::getAsObject()` will add `\stdClass` as a native return type declaration in v2.0. Do the same in your implementation now to avoid errors.
+     * @return-type-will-change \stdClass `\Art4\JsonApiClient\Input\Input::getAsObject()` will add `\stdClass` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
      *
      * This should be a native PHP stdClass object, so Manager could
      * iterate over all public attributes
@@ -25,6 +25,5 @@ interface Input
      *
      * @return \stdClass
      */
-    public function getAsObject();
-    // public function getAsObject(): \stdClass;
+    public function getAsObject()/*: \stdClass */;
 }
diff --git a/src/Manager.php b/src/Manager.php
index b22dde4..0610da0 100644
--- a/src/Manager.php
+++ b/src/Manager.php
@@ -18,36 +18,30 @@ interface Manager
     /**
      * Parse the input
      *
-     * @deprecated `\Art4\JsonApiClient\Manager::parse()` will add `\Art4\JsonApiClient\Accessable` as a native return type declaration in v2.0. Do the same in your implementation now to avoid errors.
+     * @return-type-will-change Accessable `\Art4\JsonApiClient\Manager::parse()` will add `\Art4\JsonApiClient\Accessable` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
      *
      * @throws \Art4\JsonApiClient\Exception\InputException If $input contains invalid JSON API
      * @throws \Art4\JsonApiClient\Exception\ValidationException If $input contains invalid JSON API
      *
      * @return \Art4\JsonApiClient\Accessable
      */
-    public function parse(Input $input);
-    // public function parse(Input $input): Accessable;
+    public function parse(Input $input)/*: Accessable */;
 
     /**
      * Get a factory from the manager
      *
-     * @deprecated `\Art4\JsonApiClient\Manager::getFactory()` will add `\Art4\JsonApiClient\Factory` as a native return type declaration in v2.0. Do the same in your implementation now to avoid errors.
+     * @return-type-will-change Factory `\Art4\JsonApiClient\Manager::getFactory()` will add `\Art4\JsonApiClient\Factory` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
      *
      * @return \Art4\JsonApiClient\Factory
      */
-    public function getFactory();
-    // public function getFactory(): Factory;
+    public function getFactory()/*: Factory */;
 
     /**
      * Get a param by key
      *
-     * @deprecated The `\Art4\JsonApiClient\Manager::getParam()` methods first parameter signature will be `string` in v2.0.
-     *
-     * @param string $key
-     * @param mixed  $default
+     * @param mixed $default
      *
      * @return mixed
      */
-    public function getParam($key, $default);
-    // public function getParam(string $key, $default);
+    public function getParam(string $key, $default);
 }
diff --git a/src/Manager/ErrorAbortManager.php b/src/Manager/ErrorAbortManager.php
index 996d3c5..db8567c 100644
--- a/src/Manager/ErrorAbortManager.php
+++ b/src/Manager/ErrorAbortManager.php
@@ -79,12 +79,11 @@ public function getFactory(): Factory
     /**
      * Get a param by key
      *
-     * @param string $key
-     * @param mixed  $default
+     * @param mixed $default
      *
      * @return mixed
      */
-    public function getParam($key, $default)
+    public function getParam(string $key, $default)
     {
         if (array_key_exists($key, $this->config)) {
             return $this->config[$key];
diff --git a/src/Serializer/Serializer.php b/src/Serializer/Serializer.php
index 823ebe1..3801cbd 100644
--- a/src/Serializer/Serializer.php
+++ b/src/Serializer/Serializer.php
@@ -15,9 +15,9 @@ interface Serializer
     /**
      * Serialize data
      *
-     * @deprecated `\Art4\JsonApiClient\Serializer\Serializer::serialize()` will add `?array` as a native return type declaration in v2.0. Do the same in your implementation now to avoid errors.
+     * @return-type-will-change ?array `\Art4\JsonApiClient\Serializer\Serializer::serialize()` will add `?array` as a native return type declaration in 2.0.0, do the same in your implementation now to avoid errors.
      *
      * @return array<string, mixed>|null
      */
-    public function serialize(Accessable $data);
+    public function serialize(Accessable $data)/*: ?array */;
 }
diff --git a/src/V1/Factory.php b/src/V1/Factory.php
index 78dc1dc..33efadf 100644
--- a/src/V1/Factory.php
+++ b/src/V1/Factory.php
@@ -55,10 +55,9 @@ public function __construct(array $overload = [])
     /**
      * Create a new instance of a class
      *
-     * @param string        $name
-     * @param array<mixed>  $args
+     * @param array<mixed> $args
      */
-    public function make($name, array $args = []): Accessable
+    public function make(string $name, array $args = []): Accessable
     {
         if (! isset($this->classes[$name])) {
             throw new FactoryException('"' . $name . '" is not a registered class');
diff --git a/src/V1/ResourceItemLink.php b/src/V1/ResourceItemLink.php
index 5315593..cf31ef6 100644
--- a/src/V1/ResourceItemLink.php
+++ b/src/V1/ResourceItemLink.php
@@ -57,7 +57,6 @@ public function get($key)
     /**
      * Set a link
      *
-     * @param string              $name The Name
      * @param string|object|mixed $link The Link
      */
     private function setLink(string $name, $link): void
diff --git a/src/V1/ResourceNull.php b/src/V1/ResourceNull.php
index 3d48c84..d687293 100644
--- a/src/V1/ResourceNull.php
+++ b/src/V1/ResourceNull.php
@@ -35,14 +35,13 @@ public function __construct($data, Manager $manager, Accessable $parent) {}
      *
      * @return bool false
      */
-    public function has($key)
+    public function has($key): bool
     {
         if (! is_int($key) && ! is_string($key) && (! is_object($key) || ! $key instanceof AccessKey)) {
             trigger_error(sprintf(
-                '%s::has(): Providing Argument #1 ($key) as %s is deprecated since 1.2.0, please provide as int|string|%s instead.',
+                '%s::has(): Providing Argument #1 ($key) as `%s` is deprecated since 1.2.0, please provide as `int|string` instead.',
                 get_class($this),
-                gettype($key),
-                AccessKey::class
+                gettype($key)
             ), \E_USER_DEPRECATED);
         }
 
@@ -54,7 +53,7 @@ public function has($key)
      *
      * @return array<string> Keys of all setted values
      */
-    public function getKeys()
+    public function getKeys(): array
     {
         return [];
     }
diff --git a/tests/BC/AccessableTest.php b/tests/BC/AccessableTest.php
index 7ee74b8..2a0d12c 100644
--- a/tests/BC/AccessableTest.php
+++ b/tests/BC/AccessableTest.php
@@ -15,11 +15,14 @@ class AccessableTest extends TestCase
 {
     /**
      * This test will test a custom implementation of the Accessable interface.
-     * DO NOT CHANGE THIS!
-     * Changes are only allowed by increasing the major version number.
      */
     public function testBcForAccessableInterface(): void
     {
+        /**
+         * DO NOT CHANGE THIS CLASS!
+         *
+         * This anonymous class represents an implementation in user code
+         */
         $class = new class () implements Accessable {
             /**
              * Get a value by a key
diff --git a/tests/BC/ElementTest.php b/tests/BC/ElementTest.php
index 73c28e3..c48e5ca 100644
--- a/tests/BC/ElementTest.php
+++ b/tests/BC/ElementTest.php
@@ -17,8 +17,6 @@ class ElementTest extends TestCase
 {
     /**
      * This test will test a custom implementation of the Element interface.
-     * DO NOT CHANGE THIS!
-     * Changes are only allowed by increasing the major version number.
      */
     public function testBcForElementInterface(): void
     {
@@ -26,6 +24,11 @@ public function testBcForElementInterface(): void
         $manager = $this->createMock(Manager::class);
         $parent = $this->createMock(Accessable::class);
 
+        /**
+         * DO NOT CHANGE THIS CLASS!
+         *
+         * This anonymous class represents an implementation in user code
+         */
         $class = new class ($data, $manager, $parent) implements Element {
             /**
              * Sets the manager and parent
diff --git a/tests/BC/Exception/ExceptionTest.php b/tests/BC/Exception/ExceptionTest.php
index c84d828..495427c 100644
--- a/tests/BC/Exception/ExceptionTest.php
+++ b/tests/BC/Exception/ExceptionTest.php
@@ -15,11 +15,14 @@ class ExceptionTest extends TestCase
 {
     /**
      * This test will test a custom implementation of the Exception interface.
-     * DO NOT CHANGE THIS!
-     * Changes are only allowed by increasing the major version number.
      */
     public function testBcForExceptionInterface(): void
     {
+        /**
+         * DO NOT CHANGE THIS CLASS!
+         *
+         * This anonymous class represents an implementation in user code
+         */
         $class = new class () implements Exception {};
 
         $this->assertInstanceOf(Exception::class, $class);
diff --git a/tests/BC/FactoryTest.php b/tests/BC/FactoryTest.php
index beb1ecd..253983f 100644
--- a/tests/BC/FactoryTest.php
+++ b/tests/BC/FactoryTest.php
@@ -15,11 +15,14 @@ class FactoryTest extends TestCase
 {
     /**
      * This test will test a custom implementation of the Factory interface.
-     * DO NOT CHANGE THIS!
-     * Changes are only allowed by increasing the major version number.
      */
     public function testBcForFactoryInterface(): void
     {
+        /**
+         * DO NOT CHANGE THIS CLASS!
+         *
+         * This anonymous class represents an implementation in user code
+         */
         $class = new class () implements Factory {
             /**
              * Create a new instance of a class
diff --git a/tests/BC/Input/InputTest.php b/tests/BC/Input/InputTest.php
index 1e0d0c7..16664cb 100644
--- a/tests/BC/Input/InputTest.php
+++ b/tests/BC/Input/InputTest.php
@@ -15,11 +15,14 @@ class InputTest extends TestCase
 {
     /**
      * This test will test a custom implementation of the Input interface.
-     * DO NOT CHANGE THIS!
-     * Changes are only allowed by increasing the major version number.
      */
     public function testBcForInputInterface(): void
     {
+        /**
+         * DO NOT CHANGE THIS CLASS!
+         *
+         * This anonymous class represents an implementation in user code
+         */
         $class = new class () implements Input {
             /**
              * Get the input as simple object
diff --git a/tests/BC/Input/RequestInputTest.php b/tests/BC/Input/RequestInputTest.php
index c52b939..ffc76b9 100644
--- a/tests/BC/Input/RequestInputTest.php
+++ b/tests/BC/Input/RequestInputTest.php
@@ -15,11 +15,14 @@ class RequestInputTest extends TestCase
 {
     /**
      * This test will test a custom implementation of the RequestInput interface.
-     * DO NOT CHANGE THIS!
-     * Changes are only allowed by increasing the major version number.
      */
     public function testBcForRequestInputInterface(): void
     {
+        /**
+         * DO NOT CHANGE THIS CLASS!
+         *
+         * This anonymous class represents an implementation in user code
+         */
         $class = new class () implements RequestInput {};
 
         $this->assertInstanceOf(RequestInput::class, $class);
diff --git a/tests/BC/ManagerTest.php b/tests/BC/ManagerTest.php
index 34005a8..573dfd1 100644
--- a/tests/BC/ManagerTest.php
+++ b/tests/BC/ManagerTest.php
@@ -16,11 +16,14 @@ class ManagerTest extends TestCase
 {
     /**
      * This test will test a custom implementation of the Manager interface.
-     * DO NOT CHANGE THIS!
-     * Changes are only allowed by increasing the major version number.
      */
     public function testBcForManagerInterface(): void
     {
+        /**
+         * DO NOT CHANGE THIS CLASS!
+         *
+         * This anonymous class represents an implementation in user code
+         */
         $class = new class () implements Manager {
             /**
              * Parse the input
diff --git a/tests/BC/Serializer/SerializerTest.php b/tests/BC/Serializer/SerializerTest.php
index 6ce99fd..ee82bca 100644
--- a/tests/BC/Serializer/SerializerTest.php
+++ b/tests/BC/Serializer/SerializerTest.php
@@ -16,11 +16,14 @@ class SerializerTest extends TestCase
 {
     /**
      * This test will test a custom implementation of the Serializer interface.
-     * DO NOT CHANGE THIS!
-     * Changes are only allowed by increasing the major version number.
      */
     public function testBcForSerializerInterface(): void
     {
+        /**
+         * DO NOT CHANGE THIS CLASS!
+         *
+         * This anonymous class represents an implementation in user code
+         */
         $class = new class () implements Serializer {
             /**
              * Serialize data
diff --git a/tests/Fixtures/AccessableTraitMock.php b/tests/Fixtures/AccessableTraitMock.php
new file mode 100644
index 0000000..c789b86
--- /dev/null
+++ b/tests/Fixtures/AccessableTraitMock.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2015-2023 Artur Weigandt https://wlabs.de/kontakt
+//
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+namespace Art4\JsonApiClient\Tests\Fixtures;
+
+use Art4\JsonApiClient\Accessable;
+use Art4\JsonApiClient\Helper\AccessableTrait;
+
+class AccessableTraitMock implements Accessable
+{
+    use AccessableTrait;
+}
diff --git a/tests/Fixtures/HelperTrait.php b/tests/Fixtures/HelperTrait.php
index aa0b604..aae051e 100644
--- a/tests/Fixtures/HelperTrait.php
+++ b/tests/Fixtures/HelperTrait.php
@@ -104,6 +104,21 @@ public static function jsonValuesProviderWithoutObjectAndString(): array
         return array_values($data);
     }
 
+    /**
+     * Json Values Provider but without the string and int
+     *
+     * @return array<array<mixed>>
+     */
+    public static function jsonValuesProviderWithoutStringAndInt(): array
+    {
+        $data = static::jsonValuesProvider();
+
+        unset($data[2]);
+        unset($data[3]);
+
+        return array_values($data);
+    }
+
     /**
      * Json Values as string Provider
      *
diff --git a/tests/Unit/Helper/AccessableTraitTest.php b/tests/Unit/Helper/AccessableTraitTest.php
index cda7d40..f52ef81 100644
--- a/tests/Unit/Helper/AccessableTraitTest.php
+++ b/tests/Unit/Helper/AccessableTraitTest.php
@@ -8,22 +8,29 @@
 
 namespace Art4\JsonApiClient\Tests\Unit\Helper;
 
-use Art4\JsonApiClient\Helper\AccessableTrait;
-use Art4\JsonApiClient\Accessable;
+use Art4\JsonApiClient\Exception\AccessException;
+use Art4\JsonApiClient\Tests\Fixtures\AccessableTraitMock;
+use Art4\JsonApiClient\Tests\Fixtures\HelperTrait;
 use PHPUnit\Framework\TestCase;
 
 class AccessableTraitTest extends TestCase
 {
-    public function testHasWithObjectAsKeyTriggersException(): void
+    use HelperTrait;
+
+    /**
+     * @dataProvider jsonValuesProviderWithoutStringAndInt
+     *
+     * @param mixed $key
+     */
+    public function testHasWithInvalidKeyTypeTriggersDeprecationError($key): void
     {
-        /** @var Accessable */
-        $resource = $this->getMockForTrait(AccessableTrait::class);
+        $resource = new AccessableTraitMock();
 
         // PHPUnit 10 compatible way to test trigger_error().
         set_error_handler(
-            function ($errno, $errstr): bool {
-                $this->assertStringEndsWith(
-                    '::has(): Providing Argument #1 ($key) as object is deprecated since 1.2.0, please provide as int|string|Art4\JsonApiClient\Helper\AccessKey instead.',
+            function ($errno, $errstr) use ($key): bool {
+                $this->assertSame(
+                    'Art4\JsonApiClient\Tests\Fixtures\AccessableTraitMock::has(): Providing Argument #1 ($key) as `' . gettype($key) . '` is deprecated since 1.2.0, please provide as `int|string` instead.',
                     $errstr
                 );
 
@@ -33,19 +40,23 @@ function ($errno, $errstr): bool {
             E_USER_DEPRECATED
         );
 
-        $resource->has(new \stdClass());
+        $resource->has($key);
     }
 
-    public function testHasWithArrayAsKeyTriggersException(): void
+    /**
+     * @dataProvider jsonValuesProviderWithoutStringAndInt
+     *
+     * @param mixed $key
+     */
+    public function testGetWithInvalidKeyTypeTriggersDeprecationError($key): void
     {
-        /** @var Accessable */
-        $resource = $this->getMockForTrait(AccessableTrait::class);
+        $resource = new AccessableTraitMock();
 
         // PHPUnit 10 compatible way to test trigger_error().
         set_error_handler(
-            function ($errno, $errstr): bool {
-                $this->assertStringEndsWith(
-                    '::has(): Providing Argument #1 ($key) as array is deprecated since 1.2.0, please provide as int|string|Art4\JsonApiClient\Helper\AccessKey instead.',
+            function ($errno, $errstr) use ($key): bool {
+                $this->assertSame(
+                    'Art4\JsonApiClient\Tests\Fixtures\AccessableTraitMock::get(): Providing Argument #1 ($key) as `' . gettype($key) . '` is deprecated since 1.2.0, please provide as `int|string` instead.',
                     $errstr
                 );
 
@@ -55,6 +66,10 @@ function ($errno, $errstr): bool {
             E_USER_DEPRECATED
         );
 
-        $resource->has([]);
+        try {
+            $resource->get($key);
+        } catch (AccessException $th) {
+            // ignore AccessException
+        }
     }
 }
diff --git a/tests/Unit/V1/ErrorCollectionTest.php b/tests/Unit/V1/ErrorCollectionTest.php
index eadff7d..e6fc4a1 100644
--- a/tests/Unit/V1/ErrorCollectionTest.php
+++ b/tests/Unit/V1/ErrorCollectionTest.php
@@ -49,15 +49,15 @@ public function testCreate(): void
         $this->assertSame($collection->getKeys(), [0, 1]);
 
         $this->assertFalse($collection->has('string'));
-
-        $this->assertTrue($collection->has(AccessKey::create(0)));
-
+        $this->assertTrue($collection->has(AccessKey::create('0')));
         $this->assertTrue($collection->has(0));
+
         $error = $collection->get(0);
 
         $this->assertInstanceOf(Accessable::class, $error);
 
         $this->assertTrue($collection->has(1));
+
         $error = $collection->get(1);
 
         $this->assertInstanceOf(Accessable::class, $error);
diff --git a/tests/Unit/V1/ResourceCollectionTest.php b/tests/Unit/V1/ResourceCollectionTest.php
index aed1f05..9955a9d 100644
--- a/tests/Unit/V1/ResourceCollectionTest.php
+++ b/tests/Unit/V1/ResourceCollectionTest.php
@@ -45,7 +45,7 @@ public function testCreateWithEmptyArray(): void
 
         // Test get() with various key types
         $this->assertFalse($collection->has(0));
-        $this->assertFalse($collection->has(AccessKey::create(0)));
+        $this->assertFalse($collection->has(AccessKey::create('0')));
         $this->assertFalse($collection->has('string'));
     }
 
@@ -95,6 +95,9 @@ public function testCreateWithIdentifierAndMeta(): void
 
         $this->assertInstanceOf(Accessable::class, $resource);
 
+        $this->assertSame($resource, $collection->get('0'));
+        $this->assertSame($resource, $collection->get(AccessKey::create('0')));
+
         $this->assertTrue($collection->has(1));
         $resource = $collection->get(1);
 
diff --git a/tests/Unit/V1/ResourceNullTest.php b/tests/Unit/V1/ResourceNullTest.php
index b59c69e..b476e3d 100644
--- a/tests/Unit/V1/ResourceNullTest.php
+++ b/tests/Unit/V1/ResourceNullTest.php
@@ -77,7 +77,7 @@ public function testHasWithObjectAsKeyTriggersException(): void
         set_error_handler(
             function ($errno, $errstr): bool {
                 $this->assertSame(
-                    'Art4\JsonApiClient\V1\ResourceNull::has(): Providing Argument #1 ($key) as object is deprecated since 1.2.0, please provide as int|string|Art4\JsonApiClient\Helper\AccessKey instead.',
+                    'Art4\JsonApiClient\V1\ResourceNull::has(): Providing Argument #1 ($key) as `object` is deprecated since 1.2.0, please provide as `int|string` instead.',
                     $errstr
                 );
 
@@ -102,7 +102,7 @@ public function testHasWithArrayAsKeyTriggersException(): void
         set_error_handler(
             function ($errno, $errstr): bool {
                 $this->assertSame(
-                    'Art4\JsonApiClient\V1\ResourceNull::has(): Providing Argument #1 ($key) as array is deprecated since 1.2.0, please provide as int|string|Art4\JsonApiClient\Helper\AccessKey instead.',
+                    'Art4\JsonApiClient\V1\ResourceNull::has(): Providing Argument #1 ($key) as `array` is deprecated since 1.2.0, please provide as `int|string` instead.',
                     $errstr
                 );