`next/jest` sets `NODE_ENV` to `'production'`

Run next info (available from version 12.0.8 and up)

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 21.1.0: Wed Oct 13 17:33:24 PDT 2021; root:xnu-8019.41.5~1/RELEASE_ARM64_T8101
Binaries:
  Node: 14.17.6
  npm: 8.1.4
  Yarn: 1.22.15
  pnpm: N/A
Relevant packages:
  next: 12.0.8-canary.17
  react: 17.0.2
  react-dom: 17.0.2

What version of Next.js are you using?

12.0.8-canary.17

What version of Node.js are you using?

14.17.6

What browser are you using?

N/A

What operating system are you using?

macOS 12.0.1 (21A559)

How are you deploying your application?

N/A

Describe the Bug

The next/jest preset sets NODE_ENV to 'production'.

Users familiar with Jest will expect NODE_ENV to be 'test' when running tests. The documentation says:

Set to 'test' if it’s not already set to something else.

In this case, NODE_ENV is indeed set to 'test' initially, but is replaced with 'production'. I’ve verified this simply by console logging the environment in the test setup files, and again in a test. I did take a quick look, but wasn’t able to identify the cause.

This is related to #17032 and #17903.

Expected Behavior

When running tests in Jest, NODE_ENV should be 'test'.

To Reproduce

Create a new app using the Jest example:

npx create-next-app --example with-jest with-jest-app

Add the following line to the example test:

// __tests__/index.test.tsx
console.log(process.env.NODE_ENV); // production

Run:

npm test

[ijjk]

Hi, this has been updated in v12.0.8-canary.18 of Next.js, please update and give it a try!

Note: you may need to run yarn jest --clearCache for this change to take affect.

[mrmckeb]

Thanks @ijjk!