Fix ThemeCollector Symfony 7 compatibility

tests/Collector/ThemeCollectorTest.php

@@ -0,0 +1,54 @@
+<?php
+
+/*
+ * This file is part of the Sylius package.
+ *
+ * (c) Paweł Jędrzejewski
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Sylius\Bundle\ThemeBundle\Tests\Collector;
+
+use PHPUnit\Framework\TestCase;
+use Sylius\Bundle\ThemeBundle\Collector\ThemeCollector;
+use Sylius\Bundle\ThemeBundle\Context\EmptyThemeContext;
+use Sylius\Bundle\ThemeBundle\HierarchyProvider\NoopThemeHierarchyProvider;
+use Sylius\Bundle\ThemeBundle\Loader\ThemeLoaderInterface;
+use Sylius\Bundle\ThemeBundle\Repository\InMemoryThemeRepository;
+
+class ThemeCollectorTest extends TestCase
+{
+    /**
+     * @test
+     */
+    public function it_has_no_used_theme(): void
+    {
+        $themeCollector = $this->createThemeCollector();
+
+        $this->assertNull($themeCollector->getUsedTheme());
+    }
+
+    private function createThemeCollector(): ThemeCollector
+    {
+        $themeLoader = new class () implements ThemeLoaderInterface {
+            public function load(): array
+            {
+                return [];
+            }
+        };
+
+        $themeRepository = new InMemoryThemeRepository($themeLoader);
+        $themeContext = new EmptyThemeContext();
+        $themeHierarchyProvider = new NoopThemeHierarchyProvider();
+
+        return new ThemeCollector(
+            $themeRepository,
+            $themeContext,
+            $themeHierarchyProvider,
+        );
+    }
+}