Mutator can not handle array

src/Eloquent/Model.php

@@ -251,6 +251,12 @@ public function attributesToArray()
         return $attributes;
     }
 
+    /** @inheritdoc */
+    protected function normalizeCastClassResponse($key, $value)
+    {
+        return [$key => $value];
+    }
+
     /** @inheritdoc */
     public function getCasts()
     {

tests/ModelTest.php

@@ -114,6 +114,19 @@ public function testUpdate(): void
 
         $check = User::find($user->_id);
         $this->assertEquals(20, $check->age);
+
+        $check->skills = ['PHP', 'Laravel', 'MongoDB', 'Laravel'];
+        $check->save();
+
+        $check = User::find($user->_id);
+        $this->assertCount(3,$check->skills);
+        $this->assertEquals(['PHP', 'Laravel', 'MongoDB'],$check->skills);
+
+        $check->update(['skills' => ['Git','Github','Unit testing','Github']]);
+
+        $check = User::find($user->_id);
+        $this->assertCount(3,$check->skills);
+        $this->assertEquals(['Git','Github','Unit testing'],$check->skills);
     }
 
     public function testManualStringId(): void

tests/Models/User.php

@@ -109,6 +109,14 @@ protected function username(): Attribute
         );
     }
 
+    protected function skills(): Attribute
+    {
+        return Attribute::make(
+            get: fn ($value) => $value,
+            set: fn ($values) => array_unique($values)
+        );
+    }
+
     public function prunable(): Builder
     {
         return $this->where('age', '>', 18);