diff --git a/system/DataCaster/DataCaster.php b/system/DataCaster/DataCaster.php
index 81ebe233c125..1d432179c129 100644
--- a/system/DataCaster/DataCaster.php
+++ b/system/DataCaster/DataCaster.php
@@ -28,6 +28,12 @@
 use CodeIgniter\Entity\Exceptions\CastException;
 use CodeIgniter\Exceptions\InvalidArgumentException;
 
+/**
+ * @phpstan-type cast_handlers array<string, CastInterface|class-string|EntityCastInterface>
+ *
+ * @see CodeIgniter\DataCaster\DataCasterTest
+ * @see CodeIgniter\Entity\EntityTest
+ */
 final class DataCaster
 {
     /**
@@ -38,9 +44,10 @@ final class DataCaster
     private array $types = [];
 
     /**
-     * Convert handlers
+     * Convert handlers.
      *
-     * @var array<string, class-string> [type => classname]
+     * @var         array<string, class-string> [type => classname]
+     * @phpstan-var cast_handlers
      */
     private array $castHandlers = [
         'array'     => ArrayCast::class,
@@ -59,10 +66,11 @@ final class DataCaster
     ];
 
     /**
-     * @param array<string, class-string>|null $castHandlers Custom convert handlers
-     * @param array<string, string>|null       $types        [field => type]
-     * @param object|null                      $helper       Helper object.
-     * @param bool                             $strict       Strict mode? Set to false for casts for Entity.
+     * @param         array<string, class-string>|null $castHandlers Custom convert handlers
+     * @param         array<string, string>|null       $types        [field => type]
+     * @param         object|null                      $helper       Helper object.
+     * @param         bool                             $strict       Strict mode? Set to false for casts for Entity.
+     * @phpstan-param cast_handlers|null               $castHandlers
      */
     public function __construct(
         ?array $castHandlers = null,
@@ -70,7 +78,7 @@ public function __construct(
         private readonly ?object $helper = null,
         private readonly bool $strict = true,
     ) {
-        $this->castHandlers = array_merge($this->castHandlers, $castHandlers);
+        $this->castHandlers = array_merge($this->castHandlers, $castHandlers ?? []);
 
         if ($types !== null) {
             $this->setTypes($types);
@@ -113,12 +121,16 @@ public function setTypes(array $types): static
      * Add ? at the beginning of the type (i.e. ?string) to get `null`
      * instead of casting $value when $value is null.
      *
-     * @param mixed       $value  The value to convert
-     * @param string      $field  The field name
-     * @param 'get'|'set' $method Allowed to "get" and "set"
+     * @param mixed  $value  The value to convert
+     * @param string $field  The field name
+     * @param string $method Allowed to "get" and "set"
      */
     public function castAs(mixed $value, string $field, string $method = 'get'): mixed
     {
+        if ($method !== 'get' && $method !== 'set') {
+            throw CastException::forInvalidMethod($method);
+        }
+
         // If the type is not defined, return as it is.
         if (! isset($this->types[$field])) {
             return $value;
diff --git a/system/Entity/Cast/ArrayCast.php b/system/Entity/Cast/ArrayCast.php
index 1c810645dec6..6860b41416b6 100644
--- a/system/Entity/Cast/ArrayCast.php
+++ b/system/Entity/Cast/ArrayCast.php
@@ -13,14 +13,8 @@
 
 namespace CodeIgniter\Entity\Cast;
 
-/**
- * Class ArrayCast
- */
 class ArrayCast extends BaseCast
 {
-    /**
-     * {@inheritDoc}
-     */
     public static function get($value, array $params = []): array
     {
         if (is_string($value) && (str_starts_with($value, 'a:') || str_starts_with($value, 's:'))) {
@@ -30,9 +24,6 @@ public static function get($value, array $params = []): array
         return (array) $value;
     }
 
-    /**
-     * {@inheritDoc}
-     */
     public static function set($value, array $params = []): string
     {
         return serialize($value);
diff --git a/system/Entity/Cast/BaseCast.php b/system/Entity/Cast/BaseCast.php
index 34cb28e787c5..c93e32c0537c 100644
--- a/system/Entity/Cast/BaseCast.php
+++ b/system/Entity/Cast/BaseCast.php
@@ -13,32 +13,13 @@
 
 namespace CodeIgniter\Entity\Cast;
 
-/**
- * Class BaseCast
- */
 abstract class BaseCast implements CastInterface
 {
-    /**
-     * Get
-     *
-     * @param array|bool|float|int|object|string|null $value  Data
-     * @param array                                   $params Additional param
-     *
-     * @return array|bool|float|int|object|string|null
-     */
     public static function get($value, array $params = [])
     {
         return $value;
     }
 
-    /**
-     * Set
-     *
-     * @param array|bool|float|int|object|string|null $value  Data
-     * @param array                                   $params Additional param
-     *
-     * @return array|bool|float|int|object|string|null
-     */
     public static function set($value, array $params = [])
     {
         return $value;
diff --git a/system/Entity/Cast/BooleanCast.php b/system/Entity/Cast/BooleanCast.php
index 8d95ba24b1de..7ac9f0ba37ee 100644
--- a/system/Entity/Cast/BooleanCast.php
+++ b/system/Entity/Cast/BooleanCast.php
@@ -13,14 +13,8 @@
 
 namespace CodeIgniter\Entity\Cast;
 
-/**
- * Class BooleanCast
- */
 class BooleanCast extends BaseCast
 {
-    /**
-     * {@inheritDoc}
-     */
     public static function get($value, array $params = []): bool
     {
         return (bool) $value;
diff --git a/system/Entity/Cast/CSVCast.php b/system/Entity/Cast/CSVCast.php
index 7b8be55d523c..c78a1315111a 100644
--- a/system/Entity/Cast/CSVCast.php
+++ b/system/Entity/Cast/CSVCast.php
@@ -13,22 +13,13 @@
 
 namespace CodeIgniter\Entity\Cast;
 
-/**
- * Class CSVCast
- */
 class CSVCast extends BaseCast
 {
-    /**
-     * {@inheritDoc}
-     */
     public static function get($value, array $params = []): array
     {
         return explode(',', $value);
     }
 
-    /**
-     * {@inheritDoc}
-     */
     public static function set($value, array $params = []): string
     {
         return implode(',', $value);
diff --git a/system/Entity/Cast/CastInterface.php b/system/Entity/Cast/CastInterface.php
index 9d790e8edbb9..8f837fe8014c 100644
--- a/system/Entity/Cast/CastInterface.php
+++ b/system/Entity/Cast/CastInterface.php
@@ -14,8 +14,6 @@
 namespace CodeIgniter\Entity\Cast;
 
 /**
- * Interface CastInterface
- *
  * The methods work at (1)(4) only.
  *   [App Code] --- (1) --> [Entity] --- (2) --> [Database]
  *   [App Code] <-- (4) --- [Entity] <-- (3) --- [Database]
diff --git a/system/Entity/Cast/DatetimeCast.php b/system/Entity/Cast/DatetimeCast.php
index 88b7b29267e0..72206ca883f7 100644
--- a/system/Entity/Cast/DatetimeCast.php
+++ b/system/Entity/Cast/DatetimeCast.php
@@ -17,9 +17,6 @@
 use DateTime;
 use Exception;
 
-/**
- * Class DatetimeCast
- */
 class DatetimeCast extends BaseCast
 {
     /**
diff --git a/system/Entity/Cast/FloatCast.php b/system/Entity/Cast/FloatCast.php
index 642e849e747e..1a767c0953f0 100644
--- a/system/Entity/Cast/FloatCast.php
+++ b/system/Entity/Cast/FloatCast.php
@@ -13,14 +13,8 @@
 
 namespace CodeIgniter\Entity\Cast;
 
-/**
- * Class FloatCast
- */
 class FloatCast extends BaseCast
 {
-    /**
-     * {@inheritDoc}
-     */
     public static function get($value, array $params = []): float
     {
         return (float) $value;
diff --git a/system/Entity/Cast/IntBoolCast.php b/system/Entity/Cast/IntBoolCast.php
index fb1c470e892e..94e65df8dde0 100644
--- a/system/Entity/Cast/IntBoolCast.php
+++ b/system/Entity/Cast/IntBoolCast.php
@@ -14,8 +14,6 @@
 namespace CodeIgniter\Entity\Cast;
 
 /**
- * Int Bool Cast
- *
  * DB column: int (0/1) <--> Class property: bool
  */
 final class IntBoolCast extends BaseCast
diff --git a/system/Entity/Cast/IntegerCast.php b/system/Entity/Cast/IntegerCast.php
index c0ecec732436..84bf09211c0f 100644
--- a/system/Entity/Cast/IntegerCast.php
+++ b/system/Entity/Cast/IntegerCast.php
@@ -13,14 +13,8 @@
 
 namespace CodeIgniter\Entity\Cast;
 
-/**
- * Class IntegerCast
- */
 class IntegerCast extends BaseCast
 {
-    /**
-     * {@inheritDoc}
-     */
     public static function get($value, array $params = []): int
     {
         return (int) $value;
diff --git a/system/Entity/Cast/JsonCast.php b/system/Entity/Cast/JsonCast.php
index ef389269ede4..245de29f3956 100644
--- a/system/Entity/Cast/JsonCast.php
+++ b/system/Entity/Cast/JsonCast.php
@@ -17,14 +17,8 @@
 use JsonException;
 use stdClass;
 
-/**
- * Class JsonCast
- */
 class JsonCast extends BaseCast
 {
-    /**
-     * {@inheritDoc}
-     */
     public static function get($value, array $params = [])
     {
         $associative = in_array('array', $params, true);
diff --git a/system/Entity/Cast/ObjectCast.php b/system/Entity/Cast/ObjectCast.php
index 1bee213d50a7..10affad4c80c 100644
--- a/system/Entity/Cast/ObjectCast.php
+++ b/system/Entity/Cast/ObjectCast.php
@@ -13,14 +13,8 @@
 
 namespace CodeIgniter\Entity\Cast;
 
-/**
- * Class ObjectCast
- */
 class ObjectCast extends BaseCast
 {
-    /**
-     * {@inheritDoc}
-     */
     public static function get($value, array $params = []): object
     {
         return (object) $value;
diff --git a/system/Entity/Cast/StringCast.php b/system/Entity/Cast/StringCast.php
index e4ed04b94d95..d538f4332dca 100644
--- a/system/Entity/Cast/StringCast.php
+++ b/system/Entity/Cast/StringCast.php
@@ -13,14 +13,8 @@
 
 namespace CodeIgniter\Entity\Cast;
 
-/**
- * Class StringCast
- */
 class StringCast extends BaseCast
 {
-    /**
-     * {@inheritDoc}
-     */
     public static function get($value, array $params = []): string
     {
         return (string) $value;
diff --git a/system/Entity/Cast/TimestampCast.php b/system/Entity/Cast/TimestampCast.php
index a445badec1f9..44bdf78864d1 100644
--- a/system/Entity/Cast/TimestampCast.php
+++ b/system/Entity/Cast/TimestampCast.php
@@ -15,14 +15,8 @@
 
 use CodeIgniter\Entity\Exceptions\CastException;
 
-/**
- * Class TimestampCast
- */
 class TimestampCast extends BaseCast
 {
-    /**
-     * {@inheritDoc}
-     */
     public static function get($value, array $params = [])
     {
         $value = strtotime($value);
diff --git a/system/Entity/Cast/URICast.php b/system/Entity/Cast/URICast.php
index d0d510b10919..a66bfba3ef45 100644
--- a/system/Entity/Cast/URICast.php
+++ b/system/Entity/Cast/URICast.php
@@ -15,14 +15,8 @@
 
 use CodeIgniter\HTTP\URI;
 
-/**
- * Class URICast
- */
 class URICast extends BaseCast
 {
-    /**
-     * {@inheritDoc}
-     */
     public static function get($value, array $params = []): URI
     {
         return $value instanceof URI ? $value : new URI($value);
diff --git a/tests/system/DataCaster/DataCasterTest.php b/tests/system/DataCaster/DataCasterTest.php
new file mode 100644
index 000000000000..89d3cbf40ea3
--- /dev/null
+++ b/tests/system/DataCaster/DataCasterTest.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <admin@codeigniter.com>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace CodeIgniter\DataCaster;
+
+use CodeIgniter\Entity\Exceptions\CastException;
+use CodeIgniter\Test\CIUnitTestCase;
+use PHPUnit\Framework\Attributes\Group;
+
+/**
+ * @internal
+ */
+#[Group('Others')]
+final class DataCasterTest extends CIUnitTestCase
+{
+    public function testCastInvalidMethodException(): void
+    {
+        $this->expectException(CastException::class);
+        $this->expectExceptionMessage('The "add" is invalid cast method, valid methods are: ["get", "set"].');
+
+        $dataCaster = new DataCaster();
+        $dataCaster->castAs([], 'name', 'add');
+    }
+}