diff --git a/core/tests/bootstrap.php b/core/tests/bootstrap.php
index e4272d2..65679fe 100644
--- a/core/tests/bootstrap.php
+++ b/core/tests/bootstrap.php
@@ -8,85 +8,85 @@
  */
 
 /**
- * Finds all valid module directories recursively within a given directory.
+ * Finds all valid extension directories recursively within a given directory.
  *
  * @param string $scan_directory
  *   The directory that should be recursively scanned.
  * @return array
- *   An associative array of module directories found within the scanned
- *   directory, keyed by module name.
+ *   An associative array of extension directories found within the scanned
+ *   directory, keyed by extension name.
  */
-function drupal_phpunit_find_module_directories($scan_directory) {
-  $module_directories = array();
+function drupal_phpunit_find_extension_directories($scan_directory) {
+  $extensions = array();
   $dir = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($scan_directory, \RecursiveDirectoryIterator::FOLLOW_SYMLINKS));
   foreach ($dir as $d) {
     if (strpos($d->getPathname(), 'info.yml') !== FALSE) {
-      // Cut off ".info.yml" from the filename and use that as the module name.
-      $module_directories[substr($d->getFilename(), 0, -9)] = $d->getPathInfo()->getRealPath();
+      // Cut off ".info.yml" from the filename to be used as the extension name.
+      $extensions[substr($d->getFilename(), 0, -9)] = $d->getPathInfo()->getRealPath();
     }
   }
 
-  return $module_directories;
+  return $extensions;
 }
 
 /**
- * Finds site-specific module directories given the path to the sites folder.
+ * Returns directories under which contributed extensions may exist.
  *
- * @param string $sites_path
- *   The path to the sites folder.
  * @return array
- *   An array of site-specific module directories.
+ *   An array of directories under which contributed extensions may exist.
  */
-function drupal_phpunit_find_site_module_directories($sites_path) {
-  $module_paths = array_map(function($dir) use ($sites_path) {
-    $module_dir = "$sites_path/$dir/modules";
-    if (is_dir($module_dir)) {
-     return realpath($module_dir);
-    }
-  }, scandir($sites_path));
-  return array_filter($module_paths);
+function drupal_phpunit_contrib_extension_directory_roots() {
+  $sites_path = __DIR__ . '/../../sites';
+  $paths = array();
+  // Note this also checks sites/../modules, themes, and profiles.
+  foreach (scandir($sites_path) as $site) {
+    $path = "$sites_path/$site";
+    $paths[] = is_dir("$path/modules") ? realpath("$path/modules") : NULL;
+    $paths[] = is_dir("$path/themes") ? realpath("$path/themes") : NULL;
+    $paths[] = is_dir("$path/profiles") ? realpath("$path/profiles") : NULL;
+  }
+  return array_filter($paths);
 }
 
 /**
- * Registers the namespace for each module directory with the autoloader.
+ * Registers the namespace for each extension directory with the autoloader.
  *
  * @param Composer\Autoload\ClassLoader $loader
  *   The supplied autoloader.
  * @param array $dirs
- *   An associative array of module directories, keyed by module name.
+ *   An associative array of extension directories, keyed by extension name.
  */
-function drupal_phpunit_register_module_dirs(Composer\Autoload\ClassLoader $loader, $dirs) {
-  foreach ($dirs as $module => $dir) {
+function drupal_phpunit_register_extension_dirs(Composer\Autoload\ClassLoader $loader, $dirs) {
+  foreach ($dirs as $extension => $dir) {
     $lib_path = $dir . '/lib';
     if (is_dir($lib_path)) {
-      $loader->add('Drupal\\' . $module, $lib_path);
+      $loader->add('Drupal\\' . $extension, $lib_path);
     }
     $tests_path = $dir . '/tests';
     if (is_dir($tests_path)) {
-      $loader->add('Drupal\\' . $module, $tests_path);
+      $loader->add('Drupal\\' . $extension, $tests_path);
     }
   }
 }
 
 // Start with classes in known locations.
-$loader = require __DIR__ . "/../vendor/autoload.php";
+$loader = require __DIR__ . '/../vendor/autoload.php';
 $loader->add('Drupal\\', __DIR__);
-$loader->add('Drupal\Core', __DIR__ . "/../../core/lib");
-$loader->add('Drupal\Component', __DIR__ . "/../../core/lib");
+$loader->add('Drupal\Core', __DIR__ . '/../../core/lib');
+$loader->add('Drupal\Component', __DIR__ . '/../../core/lib');
 
-// Scan for arbitrary module namespaces.
-$module_locations = array_merge(array(
-  __DIR__ . "/../modules",
-  __DIR__ . "/../../modules",
-  __DIR__ . "/../../profiles",
-  __DIR__ . "/../../themes",
-), drupal_phpunit_find_site_module_directories(__DIR__ . "/../../sites"));
+// Scan for arbitrary extension namespaces from core and contrib.
+$extension_roots = array_merge(array(
+  __DIR__ . '/../modules',
+  __DIR__ . '/../themes',
+  __DIR__ . '/../profiles',
+), drupal_phpunit_contrib_extension_directory_roots());
 
-$dirs = array_map('drupal_phpunit_find_module_directories', $module_locations);
+$dirs = array_map('drupal_phpunit_find_extension_directories', $extension_roots);
 $dirs = array_reduce($dirs, 'array_merge', array());
-drupal_phpunit_register_module_dirs($loader, $dirs);
+drupal_phpunit_register_extension_dirs($loader, $dirs);
 
-require __DIR__ . "/../../core/lib/Drupal.php";
+require __DIR__ . '/../../core/lib/Drupal.php';
 // Look into removing this later.
 define('REQUEST_TIME', (int) $_SERVER['REQUEST_TIME']);