vagrant@local:/var/www/mysite/docroot$ ../vendor/bin/phpunit -c core/phpunit.xml --group mymodule
PHP Fatal error:  Trait 'DrupalTestsfacetsFunctionalBlockTestTrait' not found in /var/www/mysite/docroot/modules/contrib/search_api_solr/tests/src/Functional/FacetsTest.php on line 20
PHP Stack trace:
PHP   1. {main}() /var/www/mysite/vendor/phpunit/phpunit/phpunit:0
PHP   2. PHPUnit_TextUI_Command::main() /var/www/mysite/vendor/phpunit/phpunit/phpunit:52
PHP   3. PHPUnit_TextUI_Command->run() /var/www/mysite/vendor/phpunit/phpunit/src/TextUI/Command.php:100
PHP   4. PHPUnit_TextUI_Command->handleArguments() /var/www/mysite/vendor/phpunit/phpunit/src/TextUI/Command.php:111
PHP   5. PHPUnit_Util_Configuration->getTestSuiteConfiguration() /var/www/mysite/vendor/phpunit/phpunit/src/TextUI/Command.php:649
PHP   6. PHPUnit_Util_Configuration->getTestSuite() /var/www/mysite/vendor/phpunit/phpunit/src/Util/Configuration.php:878
PHP   7. PHPUnit_Framework_TestSuite->addTestFile() /var/www/mysite/vendor/phpunit/phpunit/src/Util/Configuration.php:1000
PHP   8. ReflectionMethod->invoke() /var/www/mysite/vendor/phpunit/phpunit/src/Framework/TestSuite.php:353
PHP   9. DrupalTestsTestSuitesFunctionalTestSuite::suite() /var/www/mysite/vendor/phpunit/phpunit/src/Framework/TestSuite.php:353
PHP  10. DrupalTestsTestSuitesTestSuiteBase->addTestsBySuiteNamespace() /var/www/mysite/docroot/core/tests/TestSuites/FunctionalTestSuite.php:22
PHP  11. PHPUnit_Framework_TestSuite->addTestFiles() /var/www/mysite/docroot/core/tests/TestSuites/TestSuiteBase.php:55
PHP  12. PHPUnit_Framework_TestSuite->addTestFile() /var/www/mysite/vendor/phpunit/phpunit/src/Framework/TestSuite.php:384
PHP  13. PHPUnit_Util_Fileloader::checkAndLoad() /var/www/mysite/vendor/phpunit/phpunit/src/Framework/TestSuite.php:310
PHP  14. PHPUnit_Util_Fileloader::load() /var/www/mysite/vendor/phpunit/phpunit/src/Util/Fileloader.php:38
PHP  15. include_once() /var/www/mysite/vendor/phpunit/phpunit/src/Util/Fileloader.php:56

Fatal error: Trait 'DrupalTestsfacetsFunctionalBlockTestTrait' not found in /var/www/mysite/docroot/modules/contrib/search_api_solr/tests/src/Functional/FacetsTest.php on line 20

namespace DrupalTestsmymoduleFunctional;

use DrupalTestsBrowserTestBase;

/**
 * Class AuthenticationTest.
 *
 * @group mymodule
 */
class AuthenticationTest extends BrowserTestBase {

  /**
   * Required modules.
   *
   * @var array
   */
  protected static $modules = ['user', 'node'];

  public function setUp() {
    parent::setUp();

    // set config for netforum
  }

  /**
   * The superuser should not authenticate to Netforum.
   */
  public function testAdminUserUsesDrupalAuthentication() {
    $account = $this->drupalCreateUser(['administer site configuration']);
    $this->drupalLogin($account);
  }

}