Jest: TypeError: Cannot read property 'foo' of undefined

I am creating new QA issue to share my findings as I have got same error as discussed already in SO but my problem was elsewhere. Reference: Jest: TypeError: Cannot read property of undefined

I was getting error "TypeError: Cannot read property 'apiUrl' of undefined". I could not find out why. I had already set esModuleInterop and allowSyntheticDefaultImports tsconfig.json so I thought all export types are supported.

Error occurs in service consumer

import Axios from 'axios';
import config from '@/services/config.service';

const axios = Axios.create({
  baseURL: config.apiUrl || undefined,
                  ^^^^^^
  ...
});

where config services exported const config and even as default export too

export let config: AppConfig;

...

config = {...}

...

export default config;

my tsconfig.json

{
  "compilerOptions": {
    "target": "esnext",
    "module": "esnext",
    "strict": true,
    "jsx": "preserve",
    "importHelpers": true,
    "moduleResolution": "node",
    "experimentalDecorators": true,
    "resolveJsonModule": true,
    "esModuleInterop": true,
    "allowSyntheticDefaultImports": true,
    "sourceMap": true,
    "baseUrl": ".",
    "types": ["node", "webpack-env", "jest", "googlemaps"],
    "paths": {
      "@/*": ["src/*"],
    },
    "lib": ["esnext", "dom", "dom.iterable", "scripthost"],
    "skipLibCheck": true
  },
  "include": [
    "src/main.ts",
    "src/types/**/*",
    "src/WS_UIkit/src/types/**/*"
  ],
  "exclude": ["node_modules"]
}

my jest.config.js

module.exports = {
  preset: '@vue/cli-plugin-unit-jest/presets/typescript-and-babel',
  // testMatch: ['**/*.spec.[jt]s?(x)],'
  testMatch: ['**/*.spec.ts'],
  moduleNameMapper: {
    // FIXES Could not locate module @/types mapped as: .../cart/src/types.
    '^@/types$': '<rootDir>/src/types/index.d',
  },
  transformIgnorePatterns: ['node_modules/(?!(quasar|quasar/*))'],
};

my babel config

module.exports = {
  presets: ['@vue/app'],
  plugins: [
    [
      'transform-imports',
      {
        quasar: {
          transform: 'quasar/dist/babel-transforms/imports.js',
          preventFullImport: true,
        },
      },
    ],
  ],
};