learning how to test

lootalot_front/babel.config.js

@@ -1,5 +1,11 @@
 module.exports = {
   presets: [
     '@vue/app'
-  ]
+  ],
+  "presets": [["env", { "modules": false }]],
+  "env": {
+    "test": {
+      "presets": [["env", { "targets": { "node": "current" } }]]
+    }
+  }
 }

lootalot_front/package.json

@@ -7,7 +7,8 @@
     "css-watch": "npm run css-build -- --watch",
     "serve": "vue-cli-service serve",
     "build": "vue-cli-service build",
-    "lint": "vue-cli-service lint"
+    "lint": "vue-cli-service lint",
+    "test": "jest"
   },
   "main": "sass/scroll.scss",
   "dependencies": {
@@ -19,10 +20,15 @@
     "@vue/cli-plugin-babel": "^3.8.0",
     "@vue/cli-plugin-eslint": "^3.8.0",
     "@vue/cli-service": "^3.8.0",
+    "@vue/test-utils": "^1.0.0-beta.29",
     "babel-eslint": "^10.0.1",
+    "babel-jest": "^24.8.0",
+    "babel-preset-env": "^1.7.0",
     "eslint": "^5.16.0",
     "eslint-plugin-vue": "^5.0.0",
+    "jest": "^24.8.0",
     "node-sass": "^4.12.0",
+    "vue-jest": "^3.0.4",
     "vue-template-compiler": "^2.6.10"
   },
   "eslintConfig": {
@@ -47,5 +53,16 @@
   "browserslist": [
     "> 1%",
     "last 2 versions"
-  ]
+  ],
+  "jest": {
+    "moduleFileExtensions": [
+      "js",
+      "json",
+      "vue"
+    ],
+    "transform": {
+      ".*\\.(vue)$": "vue-jest",
+      "^.+\\.js$": "<rootDir>/node_modules/babel-jest"
+    }
+  }
 }

lootalot_front/src/components/NumberInput.vue

@@ -17,12 +17,10 @@
             checkError (ev) {
                 const newValue = ev.target.value;
                 this.has_error = isNaN(newValue);
-                if (!this.has_error) {
-		        this.$emit(
-		            'input',
-		            Number(newValue)
-		        );
-		}
+	        this.$emit(
+	            'input',
+	            this.has_error ? 0 : Number(newValue)
+	        );
             }
         },
     }