Inital commit after splitting from project

tests/MapWithKeysTest.php

@@ -0,0 +1,61 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tez\Utils\Tests\Arr;
+
+use PHPUnit\Framework\TestCase;
+use Tez\Utils\Arr\MapWithKeys;
+
+final class MapWithKeysTest extends TestCase
+{
+    public function testTransformsKeysAndValues(): void
+    {
+        /** @var list<array{id: int, name: string}> $users */
+        $users = [
+            ['id' => 1, 'name' => 'Alice'],
+            ['id' => 2, 'name' => 'Bob'],
+        ];
+
+        $result = MapWithKeys::map($users, function (mixed $u) {
+            /** @var array{id: int, name: string} $u */
+            return [$u['id'] => $u['name']];
+        });
+
+        self::assertSame([1 => 'Alice', 2 => 'Bob'], $result);
+    }
+
+    public function testSwapsKeyAndValue(): void
+    {
+        $result = MapWithKeys::map(['a' => 1, 'b' => 2], function (mixed $v, int|string $k) {
+            /** @var int $v */
+            return [$v => $k];
+        });
+
+        self::assertSame([1 => 'a', 2 => 'b'], $result);
+    }
+
+    public function testLastWinsOnDuplicateKey(): void
+    {
+        $result = MapWithKeys::map([1, 2, 3], fn($v) => ['key' => $v]);
+
+        self::assertSame(['key' => 3], $result);
+    }
+
+    public function testEmptyInputReturnsEmpty(): void
+    {
+        self::assertSame([], MapWithKeys::map([], fn($v) => ['x' => $v]));
+    }
+
+    public function testReceivesOriginalKey(): void
+    {
+        $received = [];
+        MapWithKeys::map(['x' => 10, 'y' => 20], function ($v, $k) use (&$received) {
+            $received[] = $k;
+
+            return [$k => $v];
+        });
+
+        self::assertSame(['x', 'y'], $received);
+    }
+}