50 AI Prompts for Testing: Jest, Vitest, and Playwright

Act as a Vitest and TypeScript testing expert.

Task:
Write Vitest unit tests for this utility function.

[paste your function here]

Test scenarios to cover:
1. Happy path: all valid inputs, verify the return value
2. Edge cases: empty input, null, undefined, zero, empty array
3. Error cases: inputs that should throw, verify the error message
4. Boundary values: minimum valid input, maximum valid input

For each test:
- Use describe block for the function name
- Use it() with a descriptive name starting with should
- Follow the Arrange, Act, Assert pattern with blank lines between stages
- Use expect().toEqual() for objects, toBe() for primitives

Use: Vitest, TypeScript — no external libraries needed

Act as a React Testing Library and Vitest expert.

Task:
Write component tests for this React component.

Component source:
[paste your component here]

Test scenarios:
1. Renders the correct initial state (check text, inputs, buttons visible)
2. User interaction: fill input, click button, check result
3. Conditional rendering: what changes when a prop flips
4. Error state: when an async action fails, error message appears
5. Loading state: spinner/skeleton visible while loading is true
6. Accessible: check ARIA roles and labels are correct

Requirements:
- Use screen queries (getByRole, getByText, getByLabelText) — no getByTestId
- Use userEvent.setup() for all user interactions
- Mock async calls with vi.mock()
- Wrap async assertions in waitFor() where needed

Use: Vitest, React Testing Library, @testing-library/user-event

Act as a Vitest mocking expert.

Task:
Write the correct mocks for this test file.

The source file under test imports:
import { fetchUser } from '../services/user.service';
import { useRouter } from 'next/navigation';
import { trackEvent } from '../lib/analytics';

Mock requirements:
1. fetchUser: mock to return a user object on the first call,
   and throw an Error on the second call

2. useRouter: mock to return an object with push: vi.fn()
   so we can assert router.push was called with the correct path

3. trackEvent: mock to do nothing but let us assert it was called
   with specific arguments

Provide:
- The vi.mock() calls with correct factory functions
- How to access the mock functions inside test cases
- How to reset mocks between tests

Use: Vitest, TypeScript

Act as a Playwright E2E testing expert.

Task:
Write Playwright tests for a user registration and login flow.

App details:
- Registration page: /register
  Fields: Name (label: Full Name), Email, Password, Confirm Password
  Submit button text: Create Account
  Success: redirects to /dashboard with welcome message
  Error: shows inline error below the field

- Login page: /login
  Fields: Email, Password
  Submit button text: Sign In
  Success: redirects to /dashboard
  Error: shows alert message Invalid credentials

Tests needed:
1. Successful registration with valid data
2. Registration fails when passwords do not match
3. Registration fails when email is already in use
4. Successful login with valid credentials
5. Login fails with wrong password
6. Redirect to /login when accessing /dashboard without auth

Use: Playwright, TypeScript, getByRole and getByLabel locators (no CSS selectors)
Include: page fixture, baseURL from playwright.config.ts, beforeEach for setup

Act as a Vitest and GitHub Actions testing expert.

Task:
Set up test coverage enforcement in GitHub Actions.

Requirements:
1. vitest.config.ts: add coverage configuration
   - Provider: v8
   - Reporters: text (for terminal), json (for CI), html (for review)
   - Include: src/**/*.{ts,tsx}
   - Exclude: src/**/*.d.ts, src/**/types.ts, src/main.tsx
   - Thresholds: lines 80%, branches 70%, functions 80%, statements 80%
   - Fail build if thresholds are not met

2. GitHub Actions workflow:
   - Trigger: push to main and pull_request to main
   - Run: npm ci, npm run test:coverage
   - Upload coverage report as workflow artifact
   - Post coverage summary as a PR comment using coverage-report-action
   - Fail the workflow if Vitest exits with a non-zero code

3. package.json scripts needed: test, test:coverage, test:ui

Use: Vitest 2, v8 coverage, GitHub Actions

Act as a Vitest and React Testing Library debugging expert.

Task:
Diagnose why this test is failing and provide the fix.

Error output:
[paste the full error message and stack trace here]

Failing test:
[paste the test code here]

Source code under test:
[paste the component or function being tested]

Mock setup (if any):
[paste vi.mock() calls and mock implementations]

Provide:
1. The root cause of the failure in plain language
2. The specific line(s) that need to change
3. The fixed test code
4. Why the fix works
5. Any related test improvements to prevent similar failures

Do not rewrite tests that are not broken — only fix what is failing.