Fixing Jest Suite Failure with import.meta.env in Vite

If you've recently encountered the error below while working with import.meta.env in a Vite-based project and running Jest tests, you're not alone:

Jest suite failed to run
error TS1343: The 'import.meta' meta-property is only allowed when the '--module' option is 'es2020', 'es2022', 'esnext', 'system', 'node12', or 'nodenext'.

This guide provides step-by-step solutions to fix this issue and ensure smooth testing with Jest.

Problem

The error occurs because Jest, by default, does not natively support the import.meta syntax. When Vite projects use import.meta.env for environment variables, Jest cannot parse or handle it properly. This causes your test suite to fail.

Solution

1. Route Environment Variables via a Constants File

A clean and simple solution is to route import.meta.env values through a constants file, which can then be mocked in tests.

Create a Constants File

// src/constants.ts
const { MODE: ENVIRONMENT } = import.meta.env

export { ENVIRONMENT }

Mock the Constants File in Tests

// example.test.ts
jest.mock('src/constants', () => ({
  ENVIRONMENT: 'development',
}))

Update Your tsconfig.json

To ensure clean imports:

{
  "compilerOptions": {
    "baseUrl": "./",
    "paths": {
      "src/*": ["src/*"]
    }
  }
}

This approach simplifies testing and eliminates the need for Jest to interpret import.meta directly.

2. Install Required Plugins

Another approach is to use plugins that enable import.meta syntax in Jest.

Install Dependencies

npm install --save-dev vite-plugin-environment babel-plugin-transform-import-meta

Update Configuration Files

babel.config.js

module.exports = {
  plugins: ['babel-plugin-transform-import-meta'],
}

tsconfig.json

{
  "compilerOptions": {
    "module": "esnext",
    "types": ["node"]
  }
}

vite.config.ts

import { defineConfig } from 'vite'
import EnvironmentPlugin from 'vite-plugin-environment'

export default defineConfig({
  plugins: [EnvironmentPlugin('all')],
})

Replace import.meta.env with process.env

For compatibility:

const ENVIRONMENT = process.env.NODE_ENV

3. Mock Environment Variables Globally

If you prefer not to use a constants file, you can mock environment variables directly in Jest.

Configure Jest to Mock Variables

jest.config.js

moduleNameMapper: {
  '^@/(.*)$': '<rootDir>/src/$1',
  '\.(css|less|scss|sass)$': 'identity-obj-proxy',
},

Add Global Mocks

setupTests.js

globalThis.importMetaEnv = {
  VITE_APP_TITLE: 'Test Title',
}

FAQs

1. Why doesn’t Jest support import.meta?

Jest uses CommonJS modules by default, while import.meta is an ES module feature. To support import.meta, you need to either mock it or enable ES module syntax in your configuration.

2. What are the advantages of routing through a constants file?

It simplifies testing, avoids repetitive mocks, and ensures that changes in environment variable logic are centralized.

3. Can I use import.meta.env directly in tests?

Not directly, unless Jest fully supports ES modules in the future. Mocking or using plugins is currently necessary.