How to go back 1 folder level with __dirname?

I am using gulp-karma and facing a simple problem but cannot seems to find what i am doing wrong .

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

Here is the code i am using and i cannot seems to go 1 level back in the folder directory . When i do the above it just append the ..\ to the folder direcotry without going 1 level back (which is the usual use of ..\). Following is the folder structure .

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

and my folder is inside the webapirole folder . i want to go back 1 folder back and go inisde the test folder which contains the karma.conf.js file. can anyone make me understand what i am doing wrong here ?

error i am getting

[18:06:32] Starting 'tdd'...
ERROR [config]: File C:\Users\Documents\WebApiRole..\test\karma.conf.js does not exist

I am using (path) NPM for the above usage......

simply require path npm in js file.Then use

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

TL;DR

Use path.join(__dirname, '..', 'test', 'karma.conf.js'). Prevent use of slashes.

Long Answer

As a lot of answers have pointed out, using path module is probably the best way. However, most of the solutions here have gone back to using slashes like:

path.join(__dirname+'../test/karma.conf.js')

However, by doing this, you're beating the purpose of using path. One uses path to do operations irrespective of the underlying OS (Linux, Windows etc). Just to give a bit of insight, you can do the path operations directly as string operations (like __dirname + '../test/karma.conf.js'. You do not do this because Linux uses forward slashes ( / ), Windows uses backward slashes ( \ ). This makes your application prone to errors when you port it across operating systems.

Thus, the better way would be:

path.join(__dirname, '..', 'test', 'karma.conf.js')

And of course, coming back - prevent use of slashes in your path.join, instead spread out your params.