refactor: enable dev config in more cases

Author: yyx990803

docs/guide/mode-and-env.md

@@ -22,7 +22,11 @@ Loaded variables will become available to all `vue-cli-service` commands, plugin
 
 An env file for a specific mode (e.g. `.env.production`) will take higher priority than a generic one (e.g. `.env`).
 
-In addition, environment variables that already exist when Vue CLI is bootstrapped have the highest priority and will not be overwritten by `.env` files. If you have a default `NODE_ENV` in your environment, you might want to consider removing it.
+In addition, environment variables that already exist when Vue CLI is bootstrapped have the highest priority and will not be overwritten by `.env` files.
+:::
+
+::: warning NODE_ENV
+If you have a default `NODE_ENV` in your environment, you should either remove it or explicitly set `NODE_ENV` when running `vue-cli-service` commands.
 :::
 
 ## Modes

packages/@vue/cli-service/lib/config/dev.js

@@ -1,6 +1,6 @@
 module.exports = (api, options) => {
   api.chainWebpack(webpackConfig => {
-    if (process.env.NODE_ENV === 'development') {
+    if (process.env.NODE_ENV !== 'production' && process.env.NODE_ENV !== 'test') {
       webpackConfig
         .devtool('cheap-module-eval-source-map')
         .output