diff --git a/tests/src/Functional/AggregatedFieldTest.php b/tests/src/Functional/AggregatedFieldTest.php
index c0e2c8e..b049319 100644
--- a/tests/src/Functional/AggregatedFieldTest.php
+++ b/tests/src/Functional/AggregatedFieldTest.php
@@ -4,6 +4,7 @@
 
 use Drupal\entity_test\Entity\EntityTestMulRevChanged;
 use Drupal\search_api\Entity\Index;
+use Drupal\search_api\Plugin\search_api\processor\Property\AggregatedFieldProperty;
 use Drupal\search_api\Utility\Utility;
 use Drupal\user\Entity\User;
 
@@ -35,15 +36,15 @@ public function setUp() {
     foreach ([7 => 'Owl', 8 => 'Robin', 9 => 'Hawk'] as $i => $value) {
       $this->users[$i] = User::create([
         'uid' => $i,
-        'name' => "User $i",
+        'name' => "User $value",
       ]);
       $this->users[$i]->save();
 
       $this->entities[$i] = EntityTestMulRevChanged::create([
         'id' => $i,
         'user_id' => $i,
-        'name' => "Test entity $i name",
-        'body' => "Test entity $i body",
+        'name' => "Test entity $value name",
+        'body' => "Test entity $value body",
       ]);
       $this->entities[$i]->save();
     }
@@ -53,9 +54,16 @@ public function setUp() {
 
     /** @var \Drupal\search_api\IndexInterface $index */
     $index = Index::load($this->indexId);
+
+    // Add the user as a datasource.
     $index->addDatasource($plugin_creation_helper->createDatasourcePlugin($index, 'entity:user'));
-    $index->addProcessor($plugin_creation_helper->createProcessorPlugin($index, 'aggregated_field'));
-    $field = $fields_helper->createField($index, 'aggregated_field', ['property_path' => 'aggregated_field']);
+
+    // Create the aggregated field property.
+    $property = AggregatedFieldProperty::create('string');
+
+    // Add and configure the aggregated field.
+    $field = $fields_helper->createFieldFromProperty($index, $property, NULL, 'aggregated_field', 'aggregated_field', 'string');
+    $field->setLabel('Aggregated field');
     $field->setConfiguration([
       'type' => 'union',
       'fields' => [
@@ -63,12 +71,11 @@ public function setUp() {
         Utility::createCombinedId('entity:user', 'name'),
       ],
     ]);
-    $field->setDataDefinition();
     $index->addField($field);
     $index->save();
-    $this->drupalGet('admin/config/search/search-api/index/');
 
-    $this->indexItems($this->indexId);
+    // Index all items, users and content.
+    $this->assertEquals(16, $this->indexItems($this->indexId));
   }
 
   /**
@@ -91,10 +98,11 @@ public function testAggregatedField() {
       'facet_source_configs[search_api:views_page__search_api_test_view__page_1][field_identifier]' => 'aggregated_field',
     ];
 
-    // Try filling out the form, but without having filled in a name for the
-    // facet to test for form errors.
+    // Try filling out the form, and configure it to use the aggregated field.
     $this->drupalPostForm(NULL, ['facet_source_id' => 'search_api:views_page__search_api_test_view__page_1'], 'Configure facet source');
     $this->drupalPostForm(NULL, $form_values, 'Save');
+
+    // Check that nothing breaks.
     $this->assertSession()->statusCodeEquals(200);
   }