diff --git a/scripts/run-tests.sh b/scripts/run-tests.sh
index 9078168..0e5ba28 100755
--- a/scripts/run-tests.sh
+++ b/scripts/run-tests.sh
@@ -142,6 +142,8 @@ All arguments are long options.
   --file      Run tests identified by specific file names, instead of group names.
               Specify the path and the extension (i.e. 'modules/user/user.test').
 
+  --directory Run all tests found within the specified file directory.
+
   --xml       <path>
 
               If provided, test results will be written as xml files to this path.
@@ -190,6 +192,7 @@ function simpletest_script_parse_args() {
     'all' => FALSE,
     'class' => FALSE,
     'file' => FALSE,
+    'directory' => NULL,
     'color' => FALSE,
     'verbose' => FALSE,
     'test_names' => array(),
@@ -451,6 +454,51 @@ function simpletest_script_get_test_list() {
         }
       }
     }
+    elseif ($args['directory']) {
+      // Extract test case class names from specified directory.
+      // Find all tests in the PSR-X structure; Drupal\$extension\Tests\*.php
+      // Since we do not want to hard-code too many structural file/directory
+      // assumptions about PSR-0/4 files and directories, we check for the
+      // minimal conditions only; i.e., a '*.php' file that has '/Tests/' in
+      // its path.
+      // Ignore anything from third party vendors, and ignore template files used in tests.
+      // And any api.php files.
+      $ignore = array('nomask' => '/vendor|\.tpl\.php|\.api\.php/');
+      $files = array();
+      if ($args['directory'][0] === '/') {
+        $directory = $args['directory'];
+      }
+      else {
+        $directory = DRUPAL_ROOT . "/" . $args['directory'];
+      }
+      $file_list = file_scan_directory($directory, '/\.php|\.test$/', $ignore);
+      foreach ($file_list as $file) {
+        // '/Tests/' can be contained anywhere in the file's path (there can be
+        // sub-directories below /Tests), but must be contained literally.
+        // Case-insensitive to match all Simpletest and PHPUnit tests:
+        //   ./lib/Drupal/foo/Tests/Bar/Baz.php
+        //   ./foo/src/Tests/Bar/Baz.php
+        //   ./foo/tests/Drupal/foo/Tests/FooTest.php
+        //   ./foo/tests/src/FooTest.php
+        // $file->filename doesn't give us a directory, so we use $file->uri
+        // Strip the drupal root directory and trailing slash off the URI
+        $filename = substr($file->uri, strlen(DRUPAL_ROOT)+1);
+        if (stripos($filename, '/Tests/')) {
+          $files[drupal_realpath($filename)] = 1;
+        } else if (stripos($filename, '.test')){
+          $files[drupal_realpath($filename)] = 1;
+        }
+      }
+
+      // Check for valid class names.
+      foreach ($all_tests as $class_name) {
+        $refclass = new ReflectionClass($class_name);
+        $classfile = $refclass->getFileName();
+        if (isset($files[$classfile])) {
+          $test_list[] = $class_name;
+        }
+      }
+    }
     else {
       // Check for valid group names and get all valid classes in group.
       foreach ($args['test_names'] as $group_name) {