Generate React Nextjs Test Suites

---
name: generate-react-nextjs-test-suites
description: "Generates unit tests, integration tests, and E2E tests for React/Next.js applications. Scans components to create Jest + React Testing Library test stubs, analyzes Istanbul/LCOV coverage reports to surface gaps, scaffolds Playwright test files from Next.js routes, mocks API call…"
category: "Web & Scraping"
author: community
version: "2.1.1"
icon: globe
---

# Senior QA Engineer

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

---

## Quick Start

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

# 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:**
```bash
# Analyze coverage report
python scripts/coverage_analyzer.py coverage/coverage-final.json

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

# 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**
```bash
python scripts/test_suite_generator.py src/components/ --scan-only
```

**Step 2: Generate test stubs**
```bash
python scripts/test_suite_generator.py src/components/ --output __tests__/
```

**Step 3: Review and customize generated tests**
```typescript
// __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-mei-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**
```bash
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**
```bash
npm test -- --coverage --coverageReporters=json
```

**Step 2: Analyze coverage gaps**
```bash
python scripts/coverage_analyzer.py coverage/coverage-final.json --threshold 80
```

**Step 3: Identify critical paths**
```bash
python scripts/coverage_analyzer.py coverage/ --critical-paths
```

**Step 4: Generate missing test stubs**
```bash
python scripts/test_suite_generator.py src/ --uncovered-only --output __tests__/
```

**Step 5: Verify improvement**
```bash
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)**
```bash
npm init playwright@latest
```

**Step 2: Scaffold E2E tests from routes**
```bash
python scripts/e2e_test_scaffolder.py src/app/ --output e2e/
```

**Step 3: Configure authentication fixtures**
```typescript
// 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**
```bash
npx playwright test
npx playwright show-report
```

**Step 5: Add to CI pipeline**
```yaml
# .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

| File | Contains | Use When |
|------|----------|----------|
| `references/testing_strategies.md` | Test pyramid, testing types, coverage targets, CI/CD integration | Designing test strategy |
| `references/test_automation_patterns.md` | Page Object Model, mocking (MSW), fixtures, async patterns | Writing test code |
| `references/qa_best_practices.md` | Testable code, flaky tests, debugging, quality metrics | Improving test quality |

---

## Common Patterns Quick Reference

### React Testing Library Queries

```typescript
// Preferred (accessible)
screen.getByRole('button', { name: "submiti"
screen.getByLabelText(/email/i)
screen.getByPlaceholderText(/search/i)

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

### Async Testing

```typescript
// 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

```typescript
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

```typescript
// Preferred
page.getByRole('button', { name: "submit" })
page.getByLabel('Email')
page.getByText('Welcome')

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

### Coverage Thresholds (jest.config.js)

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

---

## Common Commands

```bash
# 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
```