feat(validation): ArrayList rule (#745)

src/Tempest/Validation/src/Rules/ArrayList.php

@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Validation\Rules;
+
+use Attribute;
+use Tempest\Validation\Rule;
+
+#[Attribute]
+final readonly class ArrayList implements Rule
+{
+    public function isValid(mixed $value): bool
+    {
+        return is_array($value) && array_is_list($value);
+    }
+
+    public function message(): string
+    {
+        return 'Value must be a list';
+    }
+}

src/Tempest/Validation/tests/Rules/ArrayListTest.php

@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tempest\Validation\Tests\Rules;
+
+use PHPUnit\Framework\TestCase;
+use Tempest\Validation\Rules\ArrayList;
+
+/**
+ * @internal
+ */
+final class ArrayListTest extends TestCase
+{
+    public function test_array_list(): void
+    {
+        $rule = new ArrayList();
+
+        $this->assertFalse($rule->isValid(['foo' => 'bar']));
+        $this->assertTrue($rule->isValid([]));
+        $this->assertTrue($rule->isValid(['a', 'b', 'c']));
+        $this->assertFalse($rule->isValid([0 => 'a', 1 => 'b', 3 => 'c']));
+        $this->assertSame('Value must be a list', $rule->message());
+    }
+}