==> Testing 
1. Build for QA:
npm run build:qa

2. Start in QA Mode:
npm run start:qa

Explanation of the QA Scripts
build:qa: This command uses cross-env to set NODE_ENV=qa before building the app with next build. It creates a production-ready build that uses QA configurations.
start:qa: After building, this command starts the Next.js app in QA mode, again using NODE_ENV=qa to ensure it references the .env.qa file for the correct environment variables.

==> add this scripts in  package.json file
"scripts": {
  "dev": "next dev",
  "build": "next build",
  "start": "next start",
  "start:qa": "cross-env NODE_ENV=qa next start",
  "build:qa": "cross-env NODE_ENV=qa next build"
}

==> Build for Production:
For production, the steps are similar, but you’ll use the production-specific scripts:

npm run build
npm run start