.../Normalizer/TextItemBaseNormalizerTest.php      | 23 ++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/core/modules/text/tests/src/Kernel/Normalizer/TextItemBaseNormalizerTest.php b/core/modules/text/tests/src/Kernel/Normalizer/TextItemBaseNormalizerTest.php
index 426f878..e577cb6 100644
--- a/core/modules/text/tests/src/Kernel/Normalizer/TextItemBaseNormalizerTest.php
+++ b/core/modules/text/tests/src/Kernel/Normalizer/TextItemBaseNormalizerTest.php
@@ -29,6 +29,16 @@ class TextItemBaseNormalizerTest extends KernelTestBase {
   protected $serializer;
 
   /**
+   * The text format ID of the fallback format.
+   *
+   * In a non-unit test, this would be read from the 'filter.settings' config,
+   * from the 'fallback_format' key.
+   *
+   * @var string
+   */
+  static $fallbackFormatId = 'plain_text';
+
+  /**
    * {@inheritdoc}
    */
   protected function setUp() {
@@ -79,6 +89,8 @@ public function testNormalize($text_item, array $expected, $filter_config_update
     $original_entity = EntityTest::create(['field_text' => $text_item]);
     $original_entity->save();
 
+    $filter_format = FilterFormat::load(empty($text_item['format']) ? static::$fallbackFormatId : $text_item['format']);
+
     $entity = clone $original_entity;
     $context = new RenderContext();
     $data = $this->container->get('renderer')
@@ -86,15 +98,12 @@ public function testNormalize($text_item, array $expected, $filter_config_update
         return $this->serializer->normalize($entity);
 
       });
+    $cacheability = new BubbleableMetadata();
+    $cacheability->setCacheTags($filter_format->getCacheTags());
+    $this->assertEquals($cacheability, $context->pop());
     $this->assertEquals($expected, $data['field_text'][0]);
 
     if ($filter_config_update) {
-      if (empty($text_item['format'])) {
-        $filter_format = FilterFormat::load('plain_text');
-      }
-      else {
-        $filter_format = FilterFormat::load($text_item['format']);
-      }
       // Update format to see if normalization changes.
       foreach ($filter_config_update as $instance_id => $update) {
         $filter_format->setFilterConfig($instance_id, $update);
@@ -111,8 +120,6 @@ public function testNormalize($text_item, array $expected, $filter_config_update
         });
 
       $this->assertFalse($context->isEmpty());
-      $cacheability = new BubbleableMetadata();
-      $cacheability->setCacheTags($tags);
       $this->assertEquals($cacheability, $context->pop());
       $expected['processed'] = $updated_processed;
       $this->assertEquals($expected, $data['field_text'][0]);