tests fix

build/webpack.base.config.js

@@ -4,7 +4,7 @@ const FriendlyErrorsWebpackPlugin = require("friendly-errors-webpack-plugin");
 
 module.exports = env => {
   return {
-    mode: env || 'development',
+    mode: env == 'test' ? 'production' : (env || 'development'),
     target: "node",
     node: {
       __dirname: false,

package.json

@@ -159,6 +159,7 @@
     "sw-precache-webpack-plugin": "^0.11.5",
     "url-loader": "^0.6.2",
     "webpack": "^4.5.0",
+    "webpack-cli": "^2.0.14",
     "webpack-merge": "^4.1.2",
     "webpack-node-externals": "^1.7.2"
   }