Senior QA Engineer

Test automation, coverage analysis, and quality assurance patterns for React and Next.js applications.

Table of Contents

• Quick Start
• Tools Overview
  • Test Suite Generator
  • Coverage Analyzer
  • E2E Test Scaffolder
• QA Workflows
  • Unit Test Generation Workflow
  • Coverage Analysis Workflow
  • E2E Test Setup Workflow
• Reference Documentation
• Common Patterns Quick Reference

Quick Start

# Generate Jest test stubs for React components
python scripts/test_suite_generator.py src/components/ --output __tests__/

# Analyze test coverage from Jest/Istanbul reports
python scripts/coverage_analyzer.py coverage/coverage-final.json --threshold 80

# Scaffold Playwright E2E tests for Next.js routes
python scripts/e2e_test_scaffolder.py src/app/ --output e2e/

Tools Overview

1. Test Suite Generator

Scans React/TypeScript components and generates Jest + React Testing Library test stubs with proper structure.

Input: Source directory containing React components Output: Test files with describe blocks, render tests, interaction tests

Usage:

# Basic usage - scan components and generate tests
python scripts/test_suite_generator.py src/components/ --output __tests__/

# Output:
# Scanning: src/components/
# Found 24 React components
#
# Generated tests:
#   __tests__/Button.test.tsx (render, click handler, disabled state)
#   __tests__/Modal.test.tsx (render, open/close, keyboard events)
#   __tests__/Form.test.tsx (render, validation, submission)
#   ...
#
# Summary: 24 test files, 87 test cases

# Include accessibility tests
python scripts/test_suite_generator.py src/ --output __tests__/ --include-a11y

# Generate with custom template
python scripts/test_suite_generator.py src/ --template custom-template.tsx

Supported Patterns:

• Functional components with hooks
• Components with Context providers
• Components with data fetching
• Form components with validation

2. Coverage Analyzer

Parses Jest/Istanbul coverage reports and identifies gaps, uncovered branches, and provides actionable recommendations.

Input: Coverage report (JSON or LCOV format) Output: Coverage analysis with recommendations

Usage:

# Analyze coverage report
python scripts/coverage_analyzer.py coverage/coverage-final.json

# Output:
# === Coverage Analysis Report ===
# Overall: 72.4% (target: 80%)
#
# BY TYPE:
#   Statements: 74.2%
#   Branches: 68.1%
#   Functions: 71.8%
#   Lines: 73.5%
#
# CRITICAL GAPS (uncovered business logic):
#   src/services/payment.ts:45-67 - Payment processing
#   src/hooks/useAuth.ts:23-41 - Authentication flow
#
# RECOMMENDATIONS:
#   1. Add tests for payment service error handling
#   2. Cover authentication edge cases
#   3. Test form validation branches
#
# Files below threshold (80%):
#   src/components/Checkout.tsx: 45%
#   src/services/api.ts: 62%

# Enforce threshold (exit 1 if below)
python scripts/coverage_analyzer.py coverage/ --threshold 80 --strict

# Generate HTML report
python scripts/coverage_analyzer.py coverage/ --format html --output report.html

3. E2E Test Scaffolder

Scans Next.js pages/app directory and generates Playwright test files with common interactions.

Input: Next.js pages or app directory Output: Playwright test files organized by route

Usage:

# Scaffold E2E tests for Next.js App Router
python scripts/e2e_test_scaffolder.py src/app/ --output e2e/

# Output:
# Scanning: src/app/
# Found 12 routes
#
# Generated E2E tests:
#   e2e/home.spec.ts (navigation, hero section)
#   e2e/auth/login.spec.ts (form submission, validation)
#   e2e/auth/register.spec.ts (registration flow)
#   e2e/dashboard.spec.ts (authenticated routes)
#   e2e/products/[id].spec.ts (dynamic routes)
#   ...
#
# Generated: playwright.config.ts
# Generated: e2e/fixtures/auth.ts

# Include Page Object Model classes
python scripts/e2e_test_scaffolder.py src/app/ --output e2e/ --include-pom

# Generate for specific routes
python scripts/e2e_test_scaffolder.py src/app/ --routes "/login,/dashboard,/checkout"

QA Workflows

Unit Test Generation Workflow

Use when setting up tests for new or existing React components.

Step 1: Scan project for untested components

python scripts/test_suite_generator.py src/components/ --scan-only

Step 2: Generate test stubs

python scripts/test_suite_generator.py src/components/ --output __tests__/

Step 3: Review and customize generated tests

// __tests__/Button.test.tsx (generated)
import { render, screen, fireEvent } from '@testing-library/react';
import { Button } from '../src/components/Button';

describe('Button', () => {
  it('renders with label', () => {
    render(<Button>Click me</Button>);
    expect(screen.getByRole('button', { name: /click me/i })).toBeInTheDocument();
  });

  it('calls onClick when clicked', () => {
    const handleClick = jest.fn();
    render(<Button onClick={handleClick}>Click</Button>);
    fireEvent.click(screen.getByRole('button'));
    expect(handleClick).toHaveBeenCalledTimes(1);
  });

  // TODO: Add your specific test cases
});

Step 4: Run tests and check coverage

npm test -- --coverage
python scripts/coverage_analyzer.py coverage/coverage-final.json

Coverage Analysis Workflow

Use when improving test coverage or preparing for release.

Step 1: Generate coverage report

npm test -- --coverage --coverageReporters=json

Step 2: Analyze coverage gaps

python scripts/coverage_analyzer.py coverage/coverage-final.json --threshold 80

Step 3: Identify critical paths

python scripts/coverage_analyzer.py coverage/ --critical-paths

Step 4: Generate missing test stubs

python scripts/test_suite_generator.py src/ --uncovered-only --output __tests__/

Step 5: Verify improvement

npm test -- --coverage
python scripts/coverage_analyzer.py coverage/ --compare previous-coverage.json

E2E Test Setup Workflow

Use when setting up Playwright for a Next.js project.

Step 1: Initialize Playwright (if not installed)

npm init playwright@latest

Step 2: Scaffold E2E tests from routes

python scripts/e2e_test_scaffolder.py src/app/ --output e2e/

Step 3: Configure authentication fixtures

// e2e/fixtures/auth.ts (generated)
import { test as base } from '@playwright/test';

export const test = base.extend({
  authenticatedPage: async ({ page }, use) => {
    await page.goto('/login');
    await page.fill('[name="email"]', 'test@example.com');
    await page.fill('[name="password"]', 'password');
    await page.click('button[type="submit"]');
    await page.waitForURL('/dashboard');
    await use(page);
  },
});

Step 4: Run E2E tests

npx playwright test
npx playwright show-report

Step 5: Add to CI pipeline

# .github/workflows/e2e.yml
- name: Run E2E tests
  run: npx playwright test
- name: Upload report
  uses: actions/upload-artifact@v3
  with:
    name: playwright-report
    path: playwright-report/

Reference Documentation

Common Patterns Quick Reference

React Testing Library Queries

// Preferred (accessible)
screen.getByRole('button', { name: /submit/i })
screen.getByLabelText(/email/i)
screen.getByPlaceholderText(/search/i)

// Fallback
screen.getByTestId('custom-element')

Async Testing

// Wait for element
await screen.findByText(/loaded/i);

// Wait for removal
await waitForElementToBeRemoved(() => screen.queryByText(/loading/i));

// Wait for condition
await waitFor(() => {
  expect(mockFn).toHaveBeenCalled();
});

Mocking with MSW

import { rest } from 'msw';
import { setupServer } from 'msw/node';

const server = setupServer(
  rest.get('/api/users', (req, res, ctx) => {
    return res(ctx.json([{ id: 1, name: 'John' }]));
  })
);

beforeAll(() => server.listen());
afterEach(() => server.resetHandlers());
afterAll(() => server.close());

Playwright Locators

// Preferred
page.getByRole('button', { name: 'Submit' })
page.getByLabel('Email')
page.getByText('Welcome')

// Chaining
page.getByRole('listitem').filter({ hasText: 'Product' })

Coverage Thresholds (jest.config.js)

module.exports = {
  coverageThreshold: {
    global: {
      branches: 80,
      functions: 80,
      lines: 80,
      statements: 80,
    },
  },
};

Common Commands

# Jest
npm test                           # Run all tests
npm test -- --watch                # Watch mode
npm test -- --coverage             # With coverage
npm test -- Button.test.tsx        # Single file

# Playwright
npx playwright test                # Run all E2E tests
npx playwright test --ui           # UI mode
npx playwright test --debug        # Debug mode
npx playwright codegen             # Generate tests

# Coverage
npm test -- --coverage --coverageReporters=lcov,json
python scripts/coverage_analyzer.py coverage/coverage-final.json