Automatically re-order tags on save

Fixes #167

web/modules/custom/opdavies_blog/tests/src/Kernel/ReorderBlogTagsTest.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace Drupal\Tests\opdavies_blog\Kernel;
+
+use Drupal\KernelTests\Core\Entity\EntityKernelTestBase;
+use Drupal\node\Entity\Node;
+use Drupal\opdavies_blog\Entity\Node\Post;
+use Drupal\taxonomy\Entity\Vocabulary;
+use Drupal\taxonomy\TermInterface;
+use Drupal\taxonomy\VocabularyInterface;
+use Drupal\Tests\node\Traits\NodeCreationTrait;
+use Drupal\Tests\taxonomy\Traits\TaxonomyTestTrait;
+
+final class ReorderBlogTagsTest extends EntityKernelTestBase {
+
+  use NodeCreationTrait;
+  use TaxonomyTestTrait;
+
+  public static $modules = [
+    // Core.
+    'node',
+    'taxonomy',
+    'link',
+
+    // Contrib.
+    'discoverable_entity_bundle_classes',
+    'hook_event_dispatcher',
+
+    // Custom.
+    'opdavies_blog_test',
+    'opdavies_blog',
+  ];
+
+  /** @test */
+  public function it_reorders_tags_on_blog_posts_to_be_arranged_alphabetically(): void {
+    /** @var VocabularyInterface $vocabulary */
+    $vocabulary = Vocabulary::load('tags');
+
+    $this->createTerm($vocabulary, ['name' => 'Drupal']); // 1
+    $this->createTerm($vocabulary, ['name' => 'PHP']); // 2
+    $this->createTerm($vocabulary, ['name' => 'Symfony']); // 3
+
+    $post = $this->createNode([
+      'field_tags' => [3, 1, 2],
+      'type' => 'post',
+    ]);
+
+    /** @var Post $post */
+    $post = Node::load($post->id());
+
+    $this->assertSame(
+      ['Drupal', 'PHP', 'Symfony'],
+      $post->getTags()
+        ->map(fn(TermInterface $tag) => $tag->label())
+        ->toArray()
+    );
+  }
+
+  protected function setUp() {
+    parent::setUp();
+
+    $this->installConfig([
+      'filter',
+      'opdavies_blog_test',
+    ]);
+
+    $this->installEntitySchema('taxonomy_vocabulary');
+    $this->installEntitySchema('taxonomy_term');
+  }
+
+}