diff --git a/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
index c2d96d4..d6060f65 100644
--- a/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -85,10 +85,12 @@ function simpletest_theme() {
     'simpletest_test_table' => array(
       'render element' => 'table',
       'file' => 'simpletest.pages.inc',
+      'template' => 'simpletest-test-table',
     ),
     'simpletest_result_summary' => array(
-      'render element' => 'form',
+      'variables' => array('form' => NULL),
       'file' => 'simpletest.pages.inc',
+      'template' => 'simpletest-result-summary',
     ),
   );
 }
diff --git a/core/modules/simpletest/simpletest.pages.inc b/core/modules/simpletest/simpletest.pages.inc
index 61a4f82..ffc1874 100644
--- a/core/modules/simpletest/simpletest.pages.inc
+++ b/core/modules/simpletest/simpletest.pages.inc
@@ -58,7 +58,7 @@ function simpletest_test_form($form, &$form_state) {
 }
 
 /**
- * Returns HTML for a test list generated by simpletest_test_form() into a table.
+ * Preprocess variables for a test list generated by simpletest_test_form() into a table.
  *
  * @param $variables
  *   An associative array containing:
@@ -66,7 +66,7 @@ function simpletest_test_form($form, &$form_state) {
  *
  * @ingroup themeable
  */
-function theme_simpletest_test_table($variables) {
+function template_preprocess_simpletest_test_table(&$variables) {
   $table = $variables['table'];
 
   drupal_add_library('simpletest', 'drupal.simpletest');
@@ -168,12 +168,13 @@ function theme_simpletest_test_table($variables) {
   // Add js array of settings.
   drupal_add_js(array('simpleTest' => $js), 'setting');
 
-  if (empty($rows)) {
-    return '<strong>' . t('No tests to display.') . '</strong>';
-  }
-  else {
-    return theme('table', array('header' => $header, 'rows' => $rows, 'attributes' => array('id' => 'simpletest-form-table')));
-  }
+  $variables['table'] = array(
+    '#type' => 'table',
+    '#header' => $header,
+    '#rows' => $rows,
+    '#empty' => t('No tests to display.'),
+    '#attributes' => array('id' => 'simpletest-form-table'),
+  );
 }
 
 /**
@@ -274,7 +275,7 @@ function simpletest_result_form($form, &$form_state, $test_id) {
       $form['result']['summary']['#' . $assertion->status]++;
     }
     $form['result']['results'][$group]['table'] = array(
-      '#theme' => 'table',
+      '#type' => 'table',
       '#header' => $header,
       '#rows' => $rows,
     );
@@ -370,7 +371,7 @@ function simpletest_result_form_submit($form, &$form_state) {
 }
 
 /**
- * Returns HTML for the summary status of a simpletest result.
+ * Preprocess variables for the summary status of a simpletest result.
  *
  * @param $variables
  *   An associative array containing:
@@ -378,9 +379,11 @@ function simpletest_result_form_submit($form, &$form_state) {
  *
  * @ingroup themeable
  */
-function theme_simpletest_result_summary($variables) {
+function template_preprocess_simpletest_result_summary(&$variables) {
   $form = $variables['form'];
-  return '<div class="simpletest-' . ($form['#ok'] ? 'pass' : 'fail') . '">' . _simpletest_format_summary_line($form) . '</div>';
+  unset($variables['form']);
+  $variables['summary'] = _simpletest_format_summary_line($form);
+  $variables['status'] = $form['#ok'] ? 'pass' : 'fail';
 }
 
 /**
diff --git a/core/modules/simpletest/templates/simpletest-result-summary.html.twig b/core/modules/simpletest/templates/simpletest-result-summary.html.twig
new file mode 100644
index 0000000..248595b
--- /dev/null
+++ b/core/modules/simpletest/templates/simpletest-result-summary.html.twig
@@ -0,0 +1,16 @@
+{#
+/**
+ * @file
+ * Default theme implementation for the content of simpletest result summary.
+ *
+ * Available variables:
+ * - status: Pass or fail of test.
+ * - summary: Summary info of test.
+ *
+ * @see template_preprocess()
+ * @see template_preprocess_simpletest_result_summary()
+ *
+ * @ingroup themeable
+ */
+#}
+<div class="simpletest-{{ status }}>{{ summary }}</div>
diff --git a/core/modules/simpletest/templates/simpletest-test-table.html.twig b/core/modules/simpletest/templates/simpletest-test-table.html.twig
new file mode 100644
index 0000000..7c920e6
--- /dev/null
+++ b/core/modules/simpletest/templates/simpletest-test-table.html.twig
@@ -0,0 +1,15 @@
+{#
+/**
+ * @file
+ * Default theme implementation for the content of simpletest test table.
+ *
+ * Available variables:
+ * - table: A simpletest table.
+ *
+ * @see template_preprocess()
+ * @see template_preprocess_simpletest_test_table()
+ *
+ * @ingroup themeable
+ */
+#}
+{{ table }}