Fix test_prevent_empty_post_meta to work in isolation (#2628)

Author: obenland

tests/phpunit/tests/includes/class-test-post-types.php

@@ -7,7 +7,6 @@
 
 namespace Activitypub\Tests;
 
-use Activitypub\Activitypub;
 use Activitypub\Post_Types;
 
 /**
@@ -20,9 +19,9 @@ class Test_Post_Types extends \WP_UnitTestCase {
 	/**
 	 * Set up test environment.
 	 */
-	public function setUp(): void {
-		parent::setUp();
-		Activitypub::init();
+	public function set_up(): void {
+		parent::set_up();
+		Post_Types::init();
 	}
 
 	/**
@@ -33,12 +32,15 @@ public function setUp(): void {
 	public function test_prevent_empty_post_meta() {
 		$post_id = self::factory()->post->create( array( 'post_author' => 1 ) );
 
+		// Storing the default value should be prevented.
 		\update_post_meta( $post_id, 'activitypub_max_image_attachments', ACTIVITYPUB_MAX_IMAGE_ATTACHMENTS );
-		$this->assertEmpty( \get_post_meta( $post_id, 'activitypub_max_image_attachments', true ) );
-		\delete_post_meta( $post_id, 'activitypub_max_image_attachments' );
+		$this->assertFalse( \metadata_exists( 'post', $post_id, 'activitypub_max_image_attachments' ) );
 
+		// Storing a non-default value should work.
 		\update_post_meta( $post_id, 'activitypub_max_image_attachments', ACTIVITYPUB_MAX_IMAGE_ATTACHMENTS + 3 );
+		$this->assertTrue( \metadata_exists( 'post', $post_id, 'activitypub_max_image_attachments' ) );
 		$this->assertEquals( ACTIVITYPUB_MAX_IMAGE_ATTACHMENTS + 3, \get_post_meta( $post_id, 'activitypub_max_image_attachments', true ) );
+
 		\delete_post_meta( $post_id, 'activitypub_max_image_attachments' );
 	}
 }