Rename helper library to get-error-message

examples/element-factory/package.json

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+{
+  "name": "button-factory",
+  "version": "1.0.0",
+  "main": "src/index.js",
+  "type": "module",
+  "scripts": {
+    "start": "vitest --ui",
+    "test": "vitest"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/stevekinney/testing-javascript.git"
+  },
+  "author": "Steve Kinney <hello@stevekinney.net>",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/stevekinney/testing-javascript/issues"
+  },
+  "homepage": "https://github.com/stevekinney/testing-javascript#readme",
+  "devDependencies": {
+    "@vitest/ui": "^2.1.1",
+    "vite": "^5.4.5",
+    "vitest": "^2.1.1"
+  },
+  "dependencies": {
+    "lit": "^3.2.0",
+    "uuid": "^10.0.0"
+  }
+}

examples/element-factory/src/button.js

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+export function createButton() {
+  const button = document.createElement('button');
+  button.textContent = 'Click Me';
+
+  button.addEventListener('click', () => {
+    button.textContent = 'Clicked!';
+  });
+
+  return button;
+}

examples/element-factory/src/button.test.js

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+import { createButton } from './button.js';
+
+describe('createButton', () => {
+  it('should create a button element', () => {
+    const button = createButton();
+    expect(button.tagName).toBe('BUTTON');
+  });
+
+  it('should have the text "Click Me"', () => {
+    const button = createButton();
+    expect(button.textContent).toBe('Click Me');
+  });
+
+  it.todo('should change the text to "Clicked!" when clicked', async () => {});
+});

examples/element-factory/src/local-storage.test.js

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+it('should properly assign to localStorage', () => {
+  const key = 'secret';
+  const message = "It's a secret to everybody.";
+
+  localStorage.setItem(key, message);
+  expect(localStorage.getItem(key)).toBe(message);
+});

examples/element-factory/src/secret-input.js

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+function getStoredSecret() {
+  try {
+    return localStorage.getItem('secret') || '';
+  } catch {
+    return '';
+  }
+}
+
+export function createSecretInput() {
+  const id = 'secret-input';
+
+  const container = document.createElement('div');
+  const input = document.createElement('input');
+  const label = document.createElement('label');
+  const button = document.createElement('button');
+
+  input.id = id;
+  input.type = 'password';
+  input.name = 'secret';
+  input.placeholder = 'Enter your secret…';
+  input.value = getStoredSecret();
+
+  label.htmlFor = id;
+  label.textContent = 'Secret';
+
+  button.id = `${id}-button`;
+  button.textContent = 'Store Secret';
+  button.addEventListener('click', () => {
+    localStorage.setItem('secret', input.value);
+    input.value = '';
+  });
+
+  container.appendChild(label);
+  container.appendChild(input);
+  container.appendChild(button);
+
+  return container;
+}

examples/element-factory/src/secret-input.test.js

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+import { screen } from '@testing-library/dom';
+import userEvent from '@testing-library/user-event';
+import { createSecretInput } from './secret-input.js';
+
+import '@testing-library/jest-dom/vitest';
+
+describe('createSecretInput', async () => {
+  beforeEach(() => {
+    vi.spyOn(localStorage, 'getItem').mockReturnValue('test secret');
+    vi.spyOn(localStorage, 'setItem');
+
+    document.body.innerHTML = '';
+    document.body.appendChild(createSecretInput());
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it('should have loaded the secret from localStorage', async () => {
+    expect(screen.getByLabelText('Secret')).toHaveValue('test secret');
+    expect(localStorage.getItem).toHaveBeenCalledWith('secret');
+  });
+
+  it('should save the secret to localStorage', async () => {
+    const input = screen.getByLabelText('Secret');
+    const button = screen.getByText('Store Secret');
+
+    await userEvent.clear(input);
+    await userEvent.type(input, 'new secret');
+    await userEvent.click(button);
+
+    expect(localStorage.setItem).toHaveBeenCalledWith('secret', 'new secret');
+  });
+});

examples/element-factory/vitest.config.ts

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+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    environment: 'happy-dom',
+    globals: true,
+  },
+});