Prevent duplicate terms being created

Within the `PostFactory` class, ensure that when using the `withTags`
method and creating tag terms that an existing term doesn't already
exist for a given name before trying to create it.

With the previous implementation, there would be multiple terms if the
PostFactory was used multiple times with the same tag name.

Given that `PostFactory` now has a dependency on `EntityTypeManger`,
this has been added as a service within `opdavies_blog_test` and needs
to be resolved from the container before trying to use it within a test.

This commit also updates the usages in `PostTest` so that those tests
continue to work and pass.

References #3

web/modules/custom/blog/tests/modules/blog_test/opdavies_blog_test.services.yml

@@ -1,3 +1,6 @@
 services:
   Drupal\opdavies_blog\Service\PostPusher\PostPusher:
     alias: Drupal\opdavies_blog\Service\PostPusher\NullPostPusher
+
+  Drupal\opdavies_blog_test\Factory\PostFactory:
+    autowire: true

web/modules/custom/blog/tests/modules/blog_test/src/Factory/PostFactory.php

@@ -5,6 +5,9 @@ declare(strict_types=1);
 namespace Drupal\opdavies_blog_test\Factory;
 
 use Assert\Assert;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Entity\EntityStorageInterface;
+use Drupal\Core\Entity\EntityTypeManagerInterface;
 use Drupal\node\Entity\Node;
 use Drupal\opdavies_blog\Entity\Node\Post;
 use Drupal\taxonomy\Entity\Term;
@@ -13,11 +16,17 @@ use Tightenco\Collect\Support\Collection;
 
 final class PostFactory {
 
+  private EntityStorageInterface $termStorage;
+
   private Collection $tags;
 
   private string $title = 'This is a test blog post';
 
-  public function __construct() {
+  public function __construct(
+    EntityTypeManagerInterface $entityTypeManager
+  ) {
+    $this->termStorage = $entityTypeManager->getStorage('taxonomy_term');
+
     $this->tags = new Collection();
   }
 
@@ -47,15 +56,25 @@ final class PostFactory {
   }
 
   public function withTags(array $tags): self {
+    $this->tags = new Collection();
+
     foreach ($tags as $tag) {
       Assert::that($tag)->notEmpty()->string();
 
-      $this->tags->push(
-        Term::create(['vid' => 'tags', 'name' => $tag])
-      );
+      $this->tags->push($this->createOrReferenceTag($tag));
     }
 
     return $this;
   }
 
+  private function createOrReferenceTag(string $tag): EntityInterface {
+    $existingTags = $this->termStorage->loadByProperties(['name' => $tag]);
+
+    if ($existingTags) {
+      return reset($existingTags);
+    }
+
+    return Term::create(['vid' => 'tags', 'name' => $tag]);
+  }
+
 }

web/modules/custom/blog/tests/src/Kernel/Entity/Node/PostTest.php

@@ -24,14 +24,16 @@ final class PostTest extends EntityKernelTestBase {
     'opdavies_blog_test',
   ];
 
+  private PostFactory $postFactory;
+
   /** @test */
   public function it_can_determine_if_a_post_contains_a_tweet(): void {
-    $post = (new PostFactory())->create();
+    $post = $this->postFactory->create();
     $post->save();
 
     $this->assertFalse($post->hasTweet());
 
-    $post = (new PostFactory())->create([Post::FIELD_HAS_TWEET => TRUE]);
+    $post = $this->postFactory->create([Post::FIELD_HAS_TWEET => TRUE]);
     $post->save();
 
     $this->assertTrue($post->hasTweet());
@@ -39,7 +41,7 @@ final class PostTest extends EntityKernelTestBase {
 
   /** @test */
   public function it_converts_a_post_to_a_tweet(): void {
-    $post = (new PostFactory())
+    $post = $this->postFactory
       ->setTitle('Creating a custom PHPUnit command for DDEV')
       ->withTags(['Automated testing', 'DDEV', 'Drupal', 'Drupal 8', 'PHP'])
       ->create();
@@ -59,7 +61,7 @@ final class PostTest extends EntityKernelTestBase {
 
   /** @test */
   public function certain_terms_are_not_added_as_hashtags(): void {
-    $post = (new PostFactory())
+    $post = $this->postFactory
       ->setTitle('Drupal Planet should not be added as a hashtag')
       ->withTags(['Drupal', 'Drupal Planet', 'PHP'])
       ->create();
@@ -80,6 +82,8 @@ final class PostTest extends EntityKernelTestBase {
   protected function setUp() {
     parent::setUp();
 
+    $this->postFactory = $this->container->get(PostFactory::class);
+
     $this->installEntitySchema('taxonomy_term');
 
     $this->installConfig(['opdavies_blog_test']);

web/modules/custom/blog/tests/src/Kernel/RelatedPostsTest.php

@@ -9,16 +9,20 @@ use Drupal\opdavies_blog_test\Factory\PostFactory;
 
 final class RelatedPostsTest extends PostTestBase {
 
+  private PostFactory $postFactory;
+
   private RelatedPostsRepository $relatedPostsRepository;
 
   /** @test */
   public function it_returns_related_posts(): void {
-    $postA = (new PostFactory())->setTitle('Post A')
+    $postA = $this->postFactory
+      ->setTitle('Post A')
       ->withTags(['Drupal 8'])
       ->create();
     $postA->save();
 
-    $postB = (new PostFactory())->setTitle('Post B')
+    $postB = $this->postFactory
+      ->setTitle('Post B')
       ->withTags(['Drupal 8'])
       ->create();
     $postB->save();
@@ -32,6 +36,7 @@ final class RelatedPostsTest extends PostTestBase {
   protected function setUp() {
     parent::setUp();
 
+    $this->postFactory = $this->container->get(PostFactory::class);
     $this->relatedPostsRepository = $this->container->get(RelatedPostsRepository::class);
   }