如何使用__目录名返回1个文件夹级别？

gulp.task('test', function (done) {
    karma.start({
        configFile: __dirname + '..\test\' +'karma.conf.js',
        singleRun: true
    }, done);
});

parent|
      test|karma.conf.js
      webapirole|gulpfile.js

[18:06:32] Starting 'tdd'...
ERROR [config]: File C:UsersDocumentsWebApiRole..	estkarma.conf.js does not exist

let reqPath = path.join(__dirname, '../../../');//It goes three folders or directories back from given __dirname.