diff --git a/src/MediaTypeSourceFieldTrait.php b/src/MediaTypeSourceFieldTrait.php
index e7094fe..f2afdbb 100644
--- a/src/MediaTypeSourceFieldTrait.php
+++ b/src/MediaTypeSourceFieldTrait.php
@@ -67,6 +67,7 @@ trait MediaTypeSourceFieldTrait {
    */
   protected function sourceFieldConfigurationForm(array $form, FormStateInterface $form_state) {
     $source_field_info = $this->sourceFieldInfo();
+    $options = [];
 
     $allowed_field_types = $source_field_info['allowed_types'];
     /** @var \Drupal\media_entity\MediaBundleInterface $bundle */
diff --git a/tests/modules/media_entity_test_type/config/schema/media_entity_test_type.schema.yml b/tests/modules/media_entity_test_type/config/schema/media_entity_test_type.schema.yml
index 6ff7e14..257c840 100644
--- a/tests/modules/media_entity_test_type/config/schema/media_entity_test_type.schema.yml
+++ b/tests/modules/media_entity_test_type/config/schema/media_entity_test_type.schema.yml
@@ -5,3 +5,6 @@ media_entity.bundle.type.test_type:
     test_config_value:
       type: string
       label: 'Test config value'
+    source_field:
+      type: string
+      label: 'Source field'
diff --git a/tests/src/FunctionalJavascript/BundleCreationTest.php b/tests/src/FunctionalJavascript/BundleCreationTest.php
index 149a261..fd701a6 100644
--- a/tests/src/FunctionalJavascript/BundleCreationTest.php
+++ b/tests/src/FunctionalJavascript/BundleCreationTest.php
@@ -2,9 +2,6 @@
 
 namespace Drupal\Tests\media_entity\FunctionalJavascript;
 
-use Drupal\field\Entity\FieldStorageConfig;
-use Drupal\media_entity_test_type\Plugin\MediaEntity\Type\TestType;
-
 /**
  * Tests the media bundle creation.
  *
@@ -22,13 +19,6 @@ class BundleCreationTest extends MediaEntityJavascriptTestBase {
   ];
 
   /**
-   * {@inheritdoc}
-   */
-  public function setUp() {
-    parent::setUp();
-  }
-
-  /**
    * Tests the media bundle creation form.
    */
   public function testBundleCreationFormWithDefaultField() {
@@ -39,22 +29,37 @@ class BundleCreationTest extends MediaEntityJavascriptTestBase {
 
     // Fill in a label to the bundle.
     $page->fillField('label', 'Foo bundle');
+    // Wait for machine name generation. Default: waitUntilVisible(), does not
+    // work properly.
+    $this->getSession()
+      ->wait(5000, "jQuery('.machine-name-value').text() === 'foo_bundle'");
 
     // Select our test bundle type.
     $this->assertSession()->fieldExists('Type provider');
     $this->assertSession()->optionExists('Type provider', 'test_type');
     $page->selectFieldOption('Type provider', 'test_type');
     $this->waitForAjaxToFinish();
-$this->saveHtmlOutput(); // @TODO Delete me before committing.
 
     // Make sure the checkbox for creating the source field is there and save.
-    $this->assertSession()->checkboxChecked('type_configuration[test_type][create_source_field]');
+    $this->assertSession()
+      ->checkboxChecked('type_configuration[test_type][create_source_field]');
     $page->pressButton('Save media bundle');
-$this->saveHtmlOutput(); // @TODO Delete me before committing.
 
     // Check whether the source field was correctly created.
-    // @TODO Finish me.
-    $this->assertNotNull(FieldStorageConfig::loadByName('media', TestType::MEDIA_ENTITY_TEST_TYPE_DEFAULT_FIELD_NAME));
+    $this->drupalGet('admin/structure/media/manage/foo_bundle/fields');
+
+    // Check 2nd column of first data row, to be machine name for field name.
+    $this->assertSession()
+      ->elementContains('xpath', '(//table[@id="field-overview"]//tr)[2]//td[2]', 'field_media_test_type');
+    // Check 3rd column of first data row, to be correct field type.
+    $this->assertSession()
+      ->elementTextContains('xpath', '(//table[@id="field-overview"]//tr)[2]//td[3]', 'Text (plain)');
+
+    // Check that the source field is correctly assigned to media bundle.
+    $this->drupalGet('admin/structure/media/manage/foo_bundle');
+
+    $this->assertSession()
+      ->fieldValueEquals('type_configuration[test_type][source_field]', 'field_media_test_type');
   }
 
 }