diff --git a/core/modules/editor/src/Tests/EditorAdminTest.php b/core/modules/editor/src/Tests/EditorAdminTest.php
index bc25912..b4a9966 100644
--- a/core/modules/editor/src/Tests/EditorAdminTest.php
+++ b/core/modules/editor/src/Tests/EditorAdminTest.php
@@ -81,7 +81,8 @@ public function testAddEditorToExistingFormat() {
     $this->enableUnicornEditor();
     $this->drupalLogin($this->adminUser);
     $this->drupalGet('admin/config/content/formats/manage/filtered_html');
-    $edit = $this->selectUnicornEditor();
+    $edit = [];
+    $this->selectUnicornEditor($edit);
     // Configure Unicorn Editor's setting to another value.
     $edit['editor[settings][ponies_too]'] = FALSE;
     $this->drupalPostForm(NULL, $edit, t('Save configuration'));
@@ -171,7 +172,7 @@ protected function addEditorToNewFormat($format_id, $format_name) {
       'name' => $format_name,
       'format' => $format_id,
     );
-    $edit += $this->selectUnicornEditor();
+    $edit += $this->selectUnicornEditor($edit);
     $this->drupalPostForm(NULL, $edit, t('Save configuration'));
   }
 
@@ -187,10 +188,13 @@ protected function enableUnicornEditor() {
   /**
    * Tests and selects the unicorn editor.
    *
+   * @param array $edit
+   *   The edit array passed by reference.
+   *
    * @return array
    *   Returns an edit array containing the values to be posted.
    */
-  protected function selectUnicornEditor() {
+  protected function selectUnicornEditor(&$edit) {
     // Verify the <select> when a text editor is available.
     $select = $this->xpath('//select[@name="editor[editor]"]');
     $select_is_disabled = $this->xpath('//select[@name="editor[editor]" and @disabled="disabled"]');
@@ -205,7 +209,7 @@ protected function selectUnicornEditor() {
     $this->assertNoRaw(t('This option is disabled because no modules that provide a text editor are currently enabled.'), 'Description for select absent that tells users to install a text editor module.');
 
     // Select the "Unicorn Editor" editor and click the "Configure" button.
-    $edit = array(
+    $edit += array(
       'editor[editor]' => 'unicorn',
     );
     $this->drupalPostAjaxForm(NULL, $edit, 'editor_configure');