test(EntityId): add unit tests for EntityId instantiation

Includes tests for valid UUID and handling of empty string.

tests/Unit/Shared/DDD/EntityIdTest.php

@@ -0,0 +1,36 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Unit\Shared\DDD;
+
+use Shared\DDD\EntityId;
+
+covers(EntityId::class);
+
+describe('EntityId', function (): void {
+    it('can be instantiated with a valid UUID string', function (): void {
+        // GIVEN
+        $validUuid = '550e8400-e29b-41d4-a716-446655440000';
+
+        // WHEN
+        $entityId = new readonly class ($validUuid) extends EntityId
+        {
+        };
+
+        // THEN
+        expect($entityId->value)
+            ->toBe($validUuid)
+            ->and((string) $entityId)->toBe($validUuid);
+    });
+
+    it('throws a DomainException when instantiated with an empty string', function (): void {
+        // GIVEN
+        $invalidUuid = '';
+
+        // WHEN & THEN
+        expect(fn () => new readonly class ($invalidUuid) extends EntityId
+        {
+        })->toThrow(\DomainException::class);
+    });
+});