diff --git a/tests/ModuleTest.php b/tests/ModuleTest.php
new file mode 100644
index 0000000..94ac3a0
--- /dev/null
+++ b/tests/ModuleTest.php
@@ -0,0 +1,32 @@
+<?php
+
+namespace Drupal\theming;
+
+use Upal\DrupalUnitTestCase;
+
+/**
+ * Test hook and callback implementations for the theming module.
+ */
+class ModuleTest extends DrupalUnitTestCase {
+
+  /**
+   * Test that it’s possible to override the type attribute of a <script> tag.
+   */
+  public function testPreRenderScriptsOverridesType() {
+    $example_url = 'https://example.com/test.js';
+    $elements['#items'] = [
+      $example_url => [
+        'type' => 'external',
+        'defer' => FALSE,
+        'attributes' => ['type' => 'module'],
+        'data' => $example_url,
+      ],
+    ];
+    $processed_elements = \theming_pre_render_scripts($elements);
+    $this->assertEqual([
+      'type' => 'module',
+      'src' => $example_url,
+    ], $processed_elements['scripts'][1]['#attributes']);
+  }
+
+}
diff --git a/theming.module b/theming.module
index 408a437..0ff2800 100644
--- a/theming.module
+++ b/theming.module
@@ -31,3 +31,27 @@ function theming_theme_registry_alter(&$hooks) {
     $hook['preprocess functions'] = array_unique($hook['preprocess functions']);
   }
 }
+
+/**
+ * Implements hook_element_info_alter().
+ */
+function theming_element_info_alter(&$info) {
+  $info['scripts']['#pre_render'] = ['theming_pre_render_scripts'];
+}
+
+/**
+ * Wrap drupal_pre_render_scripts() to add custom attributes to script tags.
+ */
+function theming_pre_render_scripts(array $elements) {
+  $processed_elements = drupal_pre_render_scripts($elements);
+  foreach (element_children($processed_elements['scripts']) as $index) {
+    // Skip aggregated scripts.
+    if (is_string($processed_elements['scripts'][$index])) {
+      continue;
+    }
+    $attributes = &$processed_elements['scripts'][$index]['#attributes'];
+    $custom_attributes = $elements['#items'][$attributes['src']]['attributes'] ?? [];
+    $attributes = $custom_attributes + $attributes;
+  }
+  return $processed_elements;
+}