diff --git a/core/tests/bootstrap.php b/core/tests/bootstrap.php
index 4c33b2d..e5faa4a 100644
--- a/core/tests/bootstrap.php
+++ b/core/tests/bootstrap.php
@@ -7,6 +7,14 @@
  * @see phpunit.xml.dist
  */
 
+/**
+ * Finds all valid module directories recursively within a given directory.
+ *
+ * @param string $scan_directory
+ *   The directory that should be recursively scanned.
+ * @return array
+ *   An array of module directories found within the scanned directory.
+ */
 function drupal_phpunit_find_module_directories($scan_directory) {
   $module_directories = array();
   $dir = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($scan_directory, RecursiveDirectoryIterator::FOLLOW_SYMLINKS));
@@ -19,6 +27,14 @@ function drupal_phpunit_find_module_directories($scan_directory) {
   return $module_directories;
 }
 
+/**
+ * Finds site-specific module directories given the path to the sites folder.
+ *
+ * @param string $sites_path
+ *   The path to the sites folder.
+ * @return array
+ *   An array of site-specific module directories.
+ */
 function drupal_phpunit_find_site_module_directories($sites_path) {
   $module_paths = array_map(function($dir) use ($sites_path) {
     $module_dir = "$sites_path/$dir/modules";
@@ -32,12 +48,12 @@ function drupal_phpunit_find_site_module_directories($sites_path) {
 /**
  * Registers the namespace for each module directory with the autoloader.
  *
- * @param ComposerAutoloader $loader
+ * @param Composer\Autoload\ClassLoader $loader
  *   The supplied autoloader.
  * @param array $dirs
  *   An array of module directories.
  */
-function drupal_phpunit_register_module_dirs($loader, $dirs) {
+function drupal_phpunit_register_module_dirs(Composer\Autoload\ClassLoader $loader, $dirs) {
   foreach ($dirs as $dir) {
     $lib_path = $dir . '/lib';
     if (is_dir($lib_path)) {