Add Jest setup for unit testing (#731)

* install jest

* rename test script name

* test Safari detection logic

* don't expose implementation details for testing

* fix jest config

* contrib build

* don't expose impl details for testing

.all-contributorsrc

@@ -481,6 +481,15 @@
       "contributions": [
         "code"
       ]
+    },
+    {
+      "login": "souppower",
+      "name": "souppower",
+      "avatar_url": "https://avatars2.githubusercontent.com/u/19849611?v=4",
+      "profile": "https://github.com/souppower",
+      "contributions": [
+        "infra"
+      ]
     }
   ],
   "repoType": "github"

.babelrc

@@ -0,0 +1,3 @@
+{
+  "presets": ["next/babel"]
+}

.eslintrc.js

@@ -4,7 +4,7 @@ module.exports = {
     browser: true,
     es6: true,
     node: true,
-    mocha: true
+    jest: true
   },
   extends: ['eslint:recommended', 'plugin:react/recommended', 'plugin:jsx-a11y/recommended'],
   parserOptions: {

.gitignore

@@ -7,3 +7,4 @@ cypress/screenshots
 .idea
 .DS_Store
 packaged
+coverage

package.json

@@ -8,7 +8,8 @@
     "build": "next build",
     "start": "next start",
     "export": "next export",
-    "test": "npm run cy:run --",
+    "test": "jest",
+    "test:e2e": "npm run cy:run --",
     "deploy": "now",
     "prettier": "prettier --config .prettierrc --write {.,components,lib,pages}/*.js {components,lib,pages,packages}/**/*.js",
     "lint": "eslint .",
@@ -62,6 +63,7 @@
     "eslint-plugin-react": "^7.12.3",
     "eslint-plugin-react-hooks": "^1.4.0",
     "husky": "^1.3.1",
+    "jest": "^24.7.1",
     "lint-staged": "^8.1.3",
     "now": "^15.0.0",
     "wait-on": "^3.2.0"