reverted:
--- b/core/modules/responsive_image/tests/src/Functional/ResponsiveImageFieldDisplayTest.php
+++ a/core/modules/responsive_image/src/Tests/ResponsiveImageFieldDisplayTest.php
@@ -1,6 +1,6 @@
 <?php
 
+namespace Drupal\responsive_image\Tests;
-namespace Drupal\Tests\responsive_image\Functional;
 
 use Drupal\Component\Utility\Unicode;
 use Drupal\image\Tests\ImageFieldTestBase;
reverted:
--- b/core/modules/responsive_image/tests/src/Functional/ResponsiveImageFieldUiTest.php
+++ a/core/modules/responsive_image/src/Tests/ResponsiveImageFieldUiTest.php
@@ -1,10 +1,10 @@
 <?php
 
+namespace Drupal\responsive_image\Tests;
-namespace Drupal\Tests\responsive_image\Functional;
 
 
 use Drupal\field_ui\Tests\FieldUiTestTrait;
+use Drupal\simpletest\WebTestBase;
-use Drupal\Tests\BrowserTestBase;
 use Drupal\responsive_image\Entity\ResponsiveImageStyle;
 
 /**
@@ -12,7 +12,7 @@
  *
  * @group responsive_image
  */
+class ResponsiveImageFieldUiTest extends WebTestBase {
-class ResponsiveImageFieldUiTest extends BrowserTestBase {
 
   use FieldUiTestTrait;
 
@@ -55,9 +55,9 @@
     $edit = [
       'fields[field_image][type]' => 'responsive_image',
       'fields[field_image][region]' => 'content',
+      'refresh_rows' => 'field_image',
     ];
+    $this->drupalPostAjaxForm(NULL, $edit, ['op' => t('Refresh')]);
-    $this->cssSelect('input[name="refresh_rows"]')[0]->setValue('field_image');
-    $this->drupalPostForm(NULL, $edit, t('Refresh'));
     $this->assertText("Select a responsive image style.", 'The expected summary is displayed.');
 
     // Submit the form.
@@ -93,7 +93,7 @@
 
     // Click on the formatter settings button to open the formatter settings
     // form.
+    $this->drupalPostAjaxForm(NULL, [], "field_image_settings_edit");
-    $this->drupalPostForm(NULL, [], "field_image_settings_edit");
 
     // Assert that the correct fields are present.
     $fieldnames = [
@@ -107,7 +107,7 @@
       'fields[field_image][settings_edit_form][settings][responsive_image_style]' => 'style_one',
       'fields[field_image][settings_edit_form][settings][image_link]' => 'content',
     ];
+    $this->drupalPostAjaxForm(NULL, $edit, "field_image_plugin_settings_update");
-    $this->drupalPostForm(NULL, $edit, "field_image_plugin_settings_update");
 
     // Save the form to save the settings.
     $this->drupalPostForm(NULL, [], t('Save'));
@@ -116,12 +116,12 @@
 
     // Click on the formatter settings button to open the formatter settings
     // form.
+    $this->drupalPostAjaxForm(NULL, [], "field_image_settings_edit");
-    $this->drupalPostForm(NULL, [], "field_image_settings_edit");
     $edit = [
       'fields[field_image][settings_edit_form][settings][responsive_image_style]' => 'style_one',
       'fields[field_image][settings_edit_form][settings][image_link]' => 'file',
     ];
+    $this->drupalPostAjaxForm(NULL, $edit, "field_image_plugin_settings_update");
-    $this->drupalPostForm(NULL, $edit, "field_image_plugin_settings_update");
 
     // Save the form to save the third party settings.
     $this->drupalPostForm(NULL, [], t('Save'));