Mocha-webpack with Vue

mocha-setup.js

require('browser-env')()
const Vue = require('vue')

Vue.config.productionTip = false

// more options for Vue?

mocha-webpack.config.js

module.exports = {
  output: {
    // use absolute paths in sourcemaps (important for debugging via IDE)
    devtoolModuleFilenameTemplate: '[absolute-resource-path]',
    devtoolFallbackModuleFilenameTemplate: '[absolute-resource-path]?[hash]'
  },
  module: {
    rules: [
      {
        test: /\.js$|\.vue$/,
        use: {
          loader: 'istanbul-instrumenter-loader',
          options: { esModules: true }
        },
        enforce: 'post',
        exclude: /node_modules|\.spec\.js$/
      },
      {
        test: /\.vue$/,
        loader: 'vue-loader',
        exclude: /node_modules/,
        options: {
          optimizeSSR: false,
          loaders: {
            scss: ['vue-style-loader', 'css-loader']
          }
        }
      },
      {
        test: /\.js$/,
        loader: 'babel-loader',
        exclude: /node_modules/
      }
    ]
  },
  devServer: {
    historyApiFallback: true,
    noInfo: true
  },
  performance: {
    hints: false
  },
  externals: [require('webpack-node-externals')()], // in order to ignore all modules in node_modules folder
  devtool: 'inline-cheap-module-source-map',
  target: 'node' // webpack should compile node compatible code
}

package.json

{
  "scripts": {
    "test": "NODE_ENV=test nyc --clean mocha-webpack --webpack-config ./mocha-webpack.config.js --colors --require ./test/_helpers/mocha-setup.js ./test/**/*.spec.js"
  },
  "devDependencies": {
    "@vue/test-utils": "^v1.0.0-beta.16",
    "babel-preset-env": "^1.7.0",
    "babel-register": "^6.26.0",
    "browser-env": "^3.2.5",
    "chai": "^4.1.2",
    "istanbul-instrumenter-loader": "^3.0.0",
    "mocha": "^5.1.1",
    "mocha-webpack": "^1.0.1",
    "nyc": "^11.8.0",
    "vue-webpack-loaders": "^1.0.6",
    "webpack-node-externals": "^1.6.0"
  },
  "nyc": {
    "include": [
      "src/**/*.(js|vue)"
    ],
    "instrument": false,
    "sourceMap": false
  }
}

TestComponent.test.js

import { mount } from '@vue/test-utils'
import { assert } from 'chai'
import Component from '../../../../src/components/TestComponent.vue'

describe('TestComponent.vue', () => {
  it('renders', () => {
    const wrapper = mount(Component)

    assert.isTrue(
      wrapper.is(true)
    )
  })
})

Mocha works completely separate from Nuxt. Make sure the paths are correct in the code where you put these files in you project.