BABEL_ENV issue when running npm test in React App - reactjs

Question

I have the following script in the scripts block of my package.json, this requires babel via babel-register- and sets the NODE_ENV to development in order to do so.
"test": "set NODE_ENV=development&&mocha --watch --require babel-register --require jsdom-global/register --require ignore-styles --require src/tests/helpers.js src/tests/**/*.js"
I am however getting this error:
Error: Using `babel-preset-react-app` requires that you specify `NODE_ENV` or `BABEL_ENV` environment variables. Valid values are "development", "test", and "production". Instead, received:undefined.
I have tried many combinations of uninstalling, reinstalling, altering the order of requirements within my script and several other steps mentioned in the main git issue for this error.
Can anyone see any glaring error in my method here? Full package below:
"dependencies": {
"prop-types": "^15.6.2",
"react": "^16.4.1",
"react-dom": "^16.4.1",
"react-scripts": "1.1.4",
"tslib": "^1.9.3",
"typescript": "^3.0.1"
},
"scripts": {
"build-css": "node-sass-chokidar src/ -o src/",
"watch-css": "node-sass-chokidar src/ -o src/ --watch --recursive",
"start-js": "react-scripts start",
"build-ts": "set NODE_ENV=development tsc || exit 0",
"watch-ts": "tsc --watch",
"build": "react-scripts build",
"start": "npm-run-all -p build-* watch-* start-js",
"test": "set NODE_ENV=development&&mocha --watch --require babel-register --require jsdom-global/register --require ignore-styles --require src/tests/helpers.js src/tests/**/*.js",
"eject": "react-scripts eject"
},
"babel": {
"presets": [
"es2015",
"react",
"react-app"
],
"plugins": [
"transform-object-rest-spread"
]
},
"devDependencies": {
"babel-cli": "^6.26.0",
"babel-plugin-transform-object-rest-spread": "^6.26.0",
"babel-preset-es2015": "^6.24.1",
"babel-preset-stage-2": "^6.24.1",
"chai": "^4.1.2",
"enzyme": "^3.4.1",
"enzyme-adapter-react-16": "^1.2.0",
"ignore-styles": "^5.0.1",
"jsdom": "^11.12.0",
"jsdom-global": "^3.0.2",
"mocha": "^5.2.0",
"node-sass-chokidar": "^1.3.3",
"npm-run-all": "^4.1.3",
"sinon": "^6.1.5"
}

Answer 1

You're currently using set to specify your NODE_ENV variable which results in it not being available to child processes, i.e. the next command chained after the && operator, which is mocha.
If you use export instead, you'll ensure it's available to child processes.
Change the beginning of your test script to the following:
"test": "export NODE_ENV=development && mocha --watch ..."
Cross-patform:
export will only work in Bash environments. For a cross-platform solution consider utilizing cross-env to set the environment variables instead. Example:
"test": "cross-env NODE_ENV=development mocha --watch ..."
Note: export has been replaced with cross-env and the && operator is not necessary.