Inital commit after splitting from project

tests/PartitionTest.php

@@ -0,0 +1,70 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tez\Utils\Tests\Arr;
+
+use PHPUnit\Framework\TestCase;
+use Tez\Utils\Arr\Partition;
+
+final class PartitionTest extends TestCase
+{
+    public function testSplitsIntoPassAndFail(): void
+    {
+        /** @var list<int> $numbers */
+        $numbers = [1, 2, 3, 4, 5, 6];
+
+        [$even, $odd] = Partition::by($numbers, fn($n) => $n % 2 === 0);
+
+        self::assertSame([2, 4, 6], $even);
+        self::assertSame([1, 3, 5], $odd);
+    }
+
+    public function testAllPassReturnsEmptyFail(): void
+    {
+        [$pass, $fail] = Partition::by([1, 2, 3], fn() => true);
+
+        self::assertSame([1, 2, 3], $pass);
+        self::assertSame([], $fail);
+    }
+
+    public function testAllFailReturnsEmptyPass(): void
+    {
+        [$pass, $fail] = Partition::by([1, 2, 3], fn() => false);
+
+        self::assertSame([], $pass);
+        self::assertSame([1, 2, 3], $fail);
+    }
+
+    public function testEmptyArrayReturnsTwoEmptyLists(): void
+    {
+        [$pass, $fail] = Partition::by([], fn() => true);
+
+        self::assertSame([], $pass);
+        self::assertSame([], $fail);
+    }
+
+    public function testWorksWithAssocArrayItems(): void
+    {
+        $users = [
+            ['name' => 'Alice', 'active' => true],
+            ['name' => 'Bob', 'active' => false],
+            ['name' => 'Carol', 'active' => true],
+        ];
+
+        [$active, $inactive] = Partition::by($users, fn($u) => $u['active']);
+
+        self::assertCount(2, $active);
+        self::assertCount(1, $inactive);
+        self::assertSame('Alice', $active[0]['name']);
+        self::assertSame('Carol', $active[1]['name']);
+    }
+
+    public function testResultIsReindexed(): void
+    {
+        [$pass, $fail] = Partition::by([10, 20, 30, 40], fn($n) => $n > 15);
+
+        self::assertSame(0, array_key_first($pass));
+        self::assertSame(0, array_key_first($fail));
+    }
+}