diff --git a/core/modules/ckeditor/tests/src/Functional/CKEditorAdminTest.php b/core/modules/ckeditor/tests/src/Functional/CKEditorAdminTest.php
index ccb112f..4de07be 100644
--- a/core/modules/ckeditor/tests/src/Functional/CKEditorAdminTest.php
+++ b/core/modules/ckeditor/tests/src/Functional/CKEditorAdminTest.php
@@ -225,9 +225,8 @@ public function testExistingFormat() {
       'name' => 'Filtered HTML',
       'editor[editor]' => 'ckeditor',
     ];
-    $this->drupalPostAjaxForm(NULL, $edit, 'editor_configure');
-    $this->assertResponse(200);
-    $this->drupalPostForm(NULL, $edit, t('Save configuration'));
+    $this->submitForm($edit, 'editor_configure');
+    $this->submitForm($edit, t('Save configuration'));
     $this->assertResponse(200);
     $this->assertText(t('The machine-readable name is already in use. It must be unique.'));
   }
diff --git a/core/modules/system/tests/src/Functional/Form/FormTest.php b/core/modules/system/tests/src/Functional/Form/FormTest.php
index 4ec14fd..1d035b6 100644
--- a/core/modules/system/tests/src/Functional/Form/FormTest.php
+++ b/core/modules/system/tests/src/Functional/Form/FormTest.php
@@ -779,7 +779,7 @@ public function testMachineNameRequiredFormAjaxSubmit() {
     $this->drupalGet('/form-test/form-test-machine-name-validation');
 
     $edit = [];
-    $this->drupalPostForm(NULL, $edit, 'Save');
+    $this->submitForm($edit, 'Save');
     $this->assertResponse(200);
     $this->assertText('Machine-readable name field is required.');
 
@@ -788,7 +788,7 @@ public function testMachineNameRequiredFormAjaxSubmit() {
       'id' => 'machine1',
       'snack' => 'apple'
     ];
-    $this->drupalPostForm(NULL, $edit, 'Save');
+    $this->submitForm($edit, 'Save');
     $this->assertResponse(200);
     $this->assertText('The form_test_machine_name_validation_form form has been submitted successfully.');
 
@@ -797,8 +797,8 @@ public function testMachineNameRequiredFormAjaxSubmit() {
       'id' => 'duplicate',
       'snack' => 'potato',
     ];
-    $this->drupalPostAjaxForm(NULL, $edit, 'snack_configure');
-    $this->drupalPostForm(NULL, $edit, 'Save');
+    $this->submitForm($edit, 'snack_configure');
+    $this->submitForm($edit, 'Save');
     $this->assertResponse(200);
     $this->assertText('The machine-readable name is already in use. It must be unique.');
   }