Declare properties so they aren't dynamic.

tests/src/Functional/AddChildTest.php

@@ -9,13 +9,19 @@ namespace Drupal\Tests\islandora\Functional;
  */
 class AddChildTest extends IslandoraFunctionalTestBase {
 
+  /**
+   * The taxonomy term representing "Collection" items.
+   *
+   * @var \Drupal\taxonomy\TermInterface
+   */
+  protected $collectionTerm;
+
   /**
    * {@inheritdoc}
    */
   public function setUp(): void {
     parent::setUp();
 
-    $this->parent =
     $this->collectionTerm = $this->container->get('entity_type.manager')->getStorage('taxonomy_term')->create([
       'name' => 'Collection',
       'vid' => $this->testVocabulary->id(),

tests/src/Functional/JsonldSelfReferenceReactionTest.php

@@ -12,6 +12,13 @@ use function GuzzleHttp\json_decode;
  */
 class JsonldSelfReferenceReactionTest extends IslandoraFunctionalTestBase {
 
+	/**
+	 * An RDF Mapping object.
+	 *
+	 * @var \Drupal\rdf\Entity\RdfMapping
+	 */
+	protected $rdfMapping;
+
   /**
    * {@inheritdoc}
    */