code: function(browser) {
        return runner.runJsUnitTests(options.filter, browser).then(
            function(results) {
              var failedCount = results.reduce(function(prev, item) {
                return prev + (item['pass'] ? 0 : 1);
              }, 0);
              log(results.length + ' tests, ' + failedCount + ' failure(s).');
              log('[ ' + chalk.cyan(browser) + ' ] JSUnit tests: ',
                  failedCount > 0 ? chalk.red('FAILED') : chalk.green('PASSED'));
              if (failedCount > 0) {
                throw new Error();
              }
            }, finalize);
      }
docs: Run only JSUnit tests.