How to resolve aliases in mocha-webpack for laravel vue single file components

I am using vuejs in Laravel 5.7 to build an SPA. I am using mocha-webpack and vue-test-utils to write some vue component tests.

The tests can't seem to work out stylesheet imports into components. For example: I have a ExampleComponent.vue which includes the following:

</script>

<style lang="scss" scoped>

@import '@/_variables.scss';

.subpanel-control > ul > li {
    background-color: lighten($body-bg, 50);
    margin-left: 10px;
    height: 25px;
    width: 25px;
    line-height: 25px;
    color: $body-bg;
}

when running npm run test I get the following error:

Error in ./resources/assets/js/components/Panel.vue?vue&type=style&index=0&id=21f01f46&lang=scss&scoped=true&

  Module build failed (from ./node_modules/sass-loader/dist/cjs.js):

  @import '@/variables';
         ^
        Can't find stylesheet to import.
     ╷
  98 │ @import '@/variables';
     │         ^^^^^^^^^^^^^
     ╵
    stdin 98:9  root stylesheet
        in C:\Users\jjackson\Documents\projects\wave\resources\assets\js\components\Panel.vue (line 98, column 9)

I can't work out why it doesn't understand the alias @. Here is my webpack.mix.js:

let mix = require('laravel-mix');
const path = require('path');

mix.js('resources/assets/js/app.js', 'public/js')
    .sass('resources/assets/sass/app.scss', 'public/css')
    .sass('resources/assets/sass/nifty.scss', 'public/css', {
        implementation: require('node-sass')
    })
    .sass('resources/assets/sass/themes/type-b/theme-ocean.scss', 'public/css')
    .less('resources/assets/less/bootstrap-4-utilities.less', 'public/css')
    .webpackConfig({
        resolve: {
            alias: {
                '@': path.resolve('resources/assets/sass'),
                '~': path.resolve('resources/assets/js')
            }
        }
    })
    .sourceMaps();

if (mix.inProduction()) {
    mix.version();
}

Any help would be appreciated

This turned out to be a docker problem. Was trying to run npm run dev outside of the docker environment, and it was causing this error. When I ran all npm commands inside of the container everything worked fine