Remove babel environment for Jest

babel.config.js

@@ -38,8 +38,9 @@ if (BABEL_ENV === 'karma' || BABEL_ENV === 'coverage') {
   plugins.push('babel-plugin-rewire');
 }
 
-// Jest is running in node environment
-if (BABEL_ENV === 'jest') {
+// Jest is running in node environment, so we need additional plugins
+const isJest = !!process.env.JEST_WORKER_ID;
+if (isJest) {
   plugins.push('@babel/plugin-transform-modules-commonjs');
   /*
   without the following, babel-plugin-istanbul throws an error:

package.json

@@ -6,8 +6,7 @@
     "eslint": "eslint --max-warnings 0 --report-unused-disable-directives --ext .js,.vue .",
     "eslint-fix": "eslint --max-warnings 0 --report-unused-disable-directives --ext .js,.vue --fix .",
     "eslint-report": "eslint --max-warnings 0 --ext .js,.vue --format html --output-file ./eslint-report.html --no-inline-config .",
-    "jest": "BABEL_ENV=jest jest",
-    "jest-debug": "BABEL_ENV=jest node --inspect-brk node_modules/.bin/jest --runInBand",
+    "jest-debug": "node --inspect-brk node_modules/.bin/jest --runInBand",
     "jsdoc": "jsdoc -c config/jsdocs.config.js",
     "karma": "BABEL_ENV=${BABEL_ENV:=karma} karma start --single-run true config/karma.config.js",
     "karma-coverage": "BABEL_ENV=coverage karma start --single-run true config/karma.config.js",