jest

.eslintrc.json

@@ -2,7 +2,8 @@
     "env": {
         "browser": true,
         "es2020": true,
-        "node": true
+        "node": true,
+        "jest": true
     },
     "extends": ["eslint:recommended", "plugin:import/errors", "plugin:import/warnings"],
     "parserOptions": {

babel.config.js

@@ -0,0 +1 @@
+module.exports = {presets: ['@babel/preset-env']};

jest.config.js

@@ -0,0 +1,5 @@
+module.exports = {
+    transform: {
+        '^.+\\.(js|jsx)$': 'babel-jest',
+    },
+};

package.json

@@ -6,7 +6,9 @@
     "scripts": {
         "start": "webpack serve --mode=development",
         "dev": "webpack serve --mode=development --open=false",
-        "build": "webpack --mode=production"
+        "build": "webpack --mode=production",
+        "lint": "eslint -c .eslintrc.json src --fix",
+        "test": "jest"
     },
     "repository": {
         "type": "git",
@@ -20,6 +22,8 @@
     },
     "homepage": "https://github.com/vigdorov/examples-for-kids#readme",
     "devDependencies": {
+        "@babel/preset-env": "^7.26.9",
+        "babel-jest": "^29.7.0",
         "clean-webpack-plugin": "^3.0.0",
         "css-loader": "^5.0.1",
         "eslint": "^7.19.0",
@@ -28,6 +32,7 @@
         "favicons-webpack-plugin": "^5.0.1",
         "file-loader": "^6.2.0",
         "html-webpack-plugin": "^5.0.0",
+        "jest": "^29.7.0",
         "mini-css-extract-plugin": "^1.3.5",
         "webpack": "^5.21.1",
         "webpack-cli": "^4.5.0",

src/consts.test.js

@@ -0,0 +1,7 @@
+import {DIFFICULTY, START_BUTTON_EASY_ID} from './consts';
+
+describe('getDifficultyById', () => {
+    it('should return correct difficulty', () => {
+        expect(DIFFICULTY[START_BUTTON_EASY_ID]).toBe(10);
+    });
+});

src/script.js

@@ -130,7 +130,7 @@ const getExample = () => {
 
 };
 
-const getDifficultyById = id => {
+export const getDifficultyById = id => {
     return DIFFICULTY[id];
 };