Add test verifying key parameter is passed correctly in findKey closure

Agent-Logs-Url: https://github.com/voku/Arrayy/sessions/9727c001-36d7-4c06-865e-c0a76fd5012f

Co-authored-by: voku <264695+voku@users.noreply.github.com>

Author: Copilot

tests/ArrayyTest.php

@@ -3262,6 +3262,25 @@ public function testFindKey($array, $search, $result)
         static::assertSame($result, $resultMatch, 'tested:' . \print_r($array, true));
     }
 
+    public function testFindKeyWithKeyParameter()
+    {
+        // Verify that the key parameter is correctly passed to the closure
+        $array = ['a' => 10, 'b' => 20, 'c' => 30];
+        $arrayy = A::create($array);
+
+        // Find the key of the element whose key is 'b'
+        $closure = static function ($value, $key) {
+            return $key === 'b';
+        };
+        static::assertSame('b', $arrayy->findKey($closure));
+
+        // Find no element when key doesn't match
+        $closureNoMatch = static function ($value, $key) {
+            return $key === 'z';
+        };
+        static::assertFalse($arrayy->findKey($closureNoMatch));
+    }
+
     /**
      * @dataProvider firstProvider()
      *