good start

.eslintrc.json

@@ -1,14 +1,21 @@
 {
-    "env": {
-        "browser": true,
-        "es2021": true
-    },
-    "extends": "airbnb-base",
-    "parserOptions": {
-        "ecmaVersion": "latest",
-        "sourceType": "module"
-    },
-    "rules": {
-        "import/extensions": ["warn", "ignorePackages"]
-    }
+  "env": {
+    "browser": true,
+    "es2021": true,
+    "jest": true
+  },
+  "extends": "airbnb-base",
+  "parserOptions": {
+    "ecmaVersion": "latest",
+    "sourceType": "module"
+  },
+  "rules": {
+    "import/extensions": [
+      "warn",
+      "ignorePackages",
+      {
+        "js": "never"
+      }
+    ]
+  }
 }

package.json

@@ -13,7 +13,7 @@
   "type": "module",
   "scripts": {
     "start": "node src/index.js",
-    "test": "echo \"Error: no test specified\" && exit 1",
+    "test": "node --experimental-vm-modules node_modules/jest/bin/jest.js",
     "lint": "eslint src"
   },
   "engines": {

src/services/notifier/NotifierService.test.js

@@ -0,0 +1,69 @@
+// test all NotifierService methods
+import { jest } from '@jest/globals';
+import NotifierService from './NotifierService.js';
+
+const mockNotify = jest.fn();
+const mockHello = jest.fn();
+const mockGoodbye = jest.fn();
+jest.unstable_mockModule('./providers/DiscordNotifierProvider', () => ({
+  hello: mockHello,
+  goodbye: mockGoodbye,
+  notify: mockNotify,
+}));
+
+describe('NotifierService', () => {
+  const services = [
+    {
+      name: 'test',
+      notifiers: [
+        {
+          type: 'discord',
+          webhook: '1234',
+        },
+      ],
+    },
+    {
+      name: 'test2',
+      notifiers: [
+        {
+          type: 'discord',
+          webhook: '1234',
+        },
+      ],
+    },
+    {
+      name: 'test3',
+      notifiers: [
+        {
+          type: 'discord',
+          webhook: '1234',
+        },
+      ],
+    },
+  ];
+
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  describe('notify', () => {
+    it('should call notify for each notifier', () => {
+      NotifierService.notify(services[0], 'UP');
+      expect(mockNotify).toHaveBeenCalledTimes(1);
+    });
+  });
+
+  describe('hello', () => {
+    it('should call hello for each notifier', () => {
+      NotifierService.hello(services);
+      expect(mockHello).toHaveBeenCalledTimes(3);
+    });
+  });
+
+  describe('goodbye', () => {
+    it('should call goodbye for each notifier', () => {
+      NotifierService.goodbye(services);
+      expect(mockGoodbye).toHaveBeenCalledTimes(3);
+    });
+  });
+});

src/services/notifier/providers/DiscordNotifierProvider.test.js

@@ -0,0 +1,30 @@
+import { jest } from '@jest/globals';
+import { MessageBuilder, Webhook } from 'discord-webhook-node';
+import DiscordNotifierProvider from './DiscordNotifierProvider';
+
+const plop = jest.fn();
+jest.unstable_mockModule('discord-webhook-node', () => ({
+  MessageBuilder,
+  Webhook,
+}));
+
+describe('DiscordNotifierProvider', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('should notify discord', () => {
+    DiscordNotifierProvider.notify('name', 'status', { webhook: 'http://plop' });
+    expect(plop).toHaveBeenCalledTimes(1);
+  });
+
+  it('should say hello to discord', () => {
+    DiscordNotifierProvider.hello('name', { webhook: 'http://' });
+    expect(mockSend).toHaveBeenCalledTimes(1);
+  });
+
+  it('should say goodbye to discord', async () => {
+    await DiscordNotifierProvider.goodbye('name', { webhook: 'http://' });
+    expect(mockSend).toHaveBeenCalledTimes(1);
+  });
+});