如何在karma中正确导入模块？

files: [
  'path/to/module.js',
  'path/to/test.js'
]

npm install karma-webpack --save-dev

webpack: {
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['@babel/preset-env']
          }
        }
      }
    ]
  }
}

import { sum } from './path/to/module';

describe('sum function', () => {
  it('should return the sum of two numbers', () => {
    expect(sum(2, 3)).toBe(5);
  });
});