diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
index bd50c23..92361df 100644
--- a/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -920,6 +920,8 @@ protected function submitForm(array $edit, $submit, $form_html_id = NULL) {
    *   POST data.
    * @param array $options
    *   Options to be forwarded to the url generator.
+   *
+   * @return string The HTML of the rendered page.
    */
   protected function drupalPostForm($path, $edit, $submit, array $options = []) {
     if (is_object($submit)) {
@@ -938,6 +940,8 @@ protected function drupalPostForm($path, $edit, $submit, array $options = []) {
     }
 
     $this->submitForm($edit, $submit);
+
+    return $this->getSession()->getPage()->getContent();
   }
 
   /**