Debugging Drupal 8 Javascript tests

DebugTest.php

<?php

class DebugTest extends YourBrokenTest {

  /**
   * Overrides a broken test method and saves HTML at the point of failure.
   */
  public function testName() {
    try {
      parent::testName();
    }
    catch (\Exception $e) {
      file_put_contents('/Users/me/debug.html', $this->getSession()->getDriver()->getHtml('/html/body'));
      throw $e;
    }
  }

}