Bug report

Describe the bug

Currently, Next.js only supports three different values for process.env.NODE_ENV (as documented here): development, production, and test.

When running NODE_ENV='test' next build, Next.js loads the right .env.test files but fails to properly replace process.env.NODE_ENV references with test (instead of production).

Previous issues (e.g. #9123, #12772) have requested support for more environment variables. This is not what this issue is about. This is an issue with behaviour that Next.js has already documented as supported (e.g. @Timer says that test is supported in this comment).

To Reproduce

Steps to reproduce the behavior, please provide code snippets or a repository:

1. Clone this repository:

$ git clone https://github.com/nicholaschiang/env-demo && cd env-demo

2. Install dependencies:

$ yarn install

3. Build the app using the test environment:

$ yarn test:build

4. Start the app using the test environment:

$ yarn test:start

5. Visit the API route at http://localhost:3000/api/env and notice that the JSON response contains production instead of test. This is because Next.js hardcodes (i.e. replaces) the process.env.NODE_ENV variable to production when running next build. This is not ideal when you want to use the NODE_ENV variable to trigger certain behavior during tests (e.g. accessing different Algolia search indexes).

Expected behavior

When running next build with the NODE_ENV set to test, Next.js should properly replace process.env.NODE_ENV references with test instead of production.

System information

• OS: PopOS 20.x
• Version of Next.js: 9.5.3
• Version of Node.js: 12.18.3

Additional context

This can be used to switch between outside resources (e.g. using a different set of Algolia indexes than the ones used in production) during tests. While this might not be ideal, it's required when running integration tests for me (because I can't easily stub out Algolia's search capabilities).