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Zhongwei Li
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skills/cli-testing-patterns/examples/jest-advanced/README.md
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skills/cli-testing-patterns/examples/jest-advanced/README.md
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# Jest Advanced CLI Testing Example
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Advanced testing patterns for CLI applications including mocking, fixtures, and integration tests.
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## Advanced Patterns
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### 1. Async Command Testing
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```typescript
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import { spawn } from 'child_process';
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async function runCLIAsync(args: string[]): Promise<CLIResult> {
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return new Promise((resolve) => {
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const child = spawn(CLI_PATH, args, { stdio: 'pipe' });
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let stdout = '';
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let stderr = '';
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child.stdout?.on('data', (data) => {
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stdout += data.toString();
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});
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child.stderr?.on('data', (data) => {
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stderr += data.toString();
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});
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child.on('close', (code) => {
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resolve({ stdout, stderr, code: code || 0 });
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});
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});
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}
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test('should handle long-running command', async () => {
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const result = await runCLIAsync(['deploy', 'production']);
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expect(result.code).toBe(0);
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}, 30000); // 30 second timeout
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```
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### 2. Environment Variable Mocking
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```typescript
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describe('environment configuration', () => {
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const originalEnv = { ...process.env };
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afterEach(() => {
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process.env = { ...originalEnv };
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});
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test('should use API key from environment', () => {
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process.env.API_KEY = 'test_key_123';
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const { stdout, code } = runCLI('status');
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expect(code).toBe(0);
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expect(stdout).toContain('Authenticated');
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});
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test('should fail without API key', () => {
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delete process.env.API_KEY;
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const { stderr, code } = runCLI('status');
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expect(code).toBe(1);
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expect(stderr).toContain('API key not found');
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});
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});
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```
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### 3. File System Fixtures
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```typescript
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import fs from 'fs';
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import os from 'os';
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describe('config file handling', () => {
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let tempDir: string;
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beforeEach(() => {
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tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'cli-test-'));
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});
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afterEach(() => {
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fs.rmSync(tempDir, { recursive: true, force: true });
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});
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test('should create config file', () => {
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const configFile = path.join(tempDir, '.config');
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const result = runCLI(`init --config ${configFile}`);
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expect(result.code).toBe(0);
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expect(fs.existsSync(configFile)).toBe(true);
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const config = JSON.parse(fs.readFileSync(configFile, 'utf8'));
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expect(config).toHaveProperty('api_key');
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});
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});
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```
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### 4. Mocking External APIs
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```typescript
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import nock from 'nock';
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describe('API interaction', () => {
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beforeEach(() => {
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nock.cleanAll();
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});
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test('should fetch deployment status', () => {
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nock('https://api.example.com')
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.get('/deployments/123')
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.reply(200, { status: 'success', environment: 'production' });
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const { stdout, code } = runCLI('status --deployment 123');
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expect(code).toBe(0);
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expect(stdout).toContain('success');
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expect(stdout).toContain('production');
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});
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test('should handle API errors', () => {
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nock('https://api.example.com')
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.get('/deployments/123')
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.reply(500, { error: 'Internal Server Error' });
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const { stderr, code } = runCLI('status --deployment 123');
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expect(code).toBe(1);
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expect(stderr).toContain('API error');
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});
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});
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```
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### 5. Test Fixtures
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```typescript
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// test-fixtures.ts
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export const createTestFixtures = () => {
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const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'cli-test-'));
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// Create sample project structure
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fs.mkdirSync(path.join(tempDir, 'src'));
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fs.writeFileSync(
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path.join(tempDir, 'package.json'),
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JSON.stringify({ name: 'test-project', version: '1.0.0' })
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);
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return {
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tempDir,
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cleanup: () => fs.rmSync(tempDir, { recursive: true, force: true }),
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};
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};
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// Usage in tests
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test('should build project', () => {
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const fixtures = createTestFixtures();
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try {
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const result = runCLI(`build --cwd ${fixtures.tempDir}`);
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expect(result.code).toBe(0);
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expect(fs.existsSync(path.join(fixtures.tempDir, 'dist'))).toBe(true);
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} finally {
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fixtures.cleanup();
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}
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});
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```
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### 6. Snapshot Testing
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```typescript
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test('help output matches snapshot', () => {
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const { stdout } = runCLI('--help');
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expect(stdout).toMatchSnapshot();
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});
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test('version format matches snapshot', () => {
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const { stdout } = runCLI('--version');
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expect(stdout).toMatchSnapshot();
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});
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```
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### 7. Parameterized Tests
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```typescript
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describe.each([
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['development', 'dev.example.com'],
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['staging', 'staging.example.com'],
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['production', 'api.example.com'],
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])('deploy to %s', (environment, expectedUrl) => {
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test(`should deploy to ${environment}`, () => {
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const { stdout, code } = runCLI(`deploy ${environment}`);
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expect(code).toBe(0);
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expect(stdout).toContain(expectedUrl);
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});
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});
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```
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### 8. Interactive Command Testing
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```typescript
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import { Readable, Writable } from 'stream';
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test('should handle interactive prompts', (done) => {
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const child = spawn(CLI_PATH, ['init'], { stdio: 'pipe' });
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const inputs = ['my-project', 'John Doe', 'john@example.com'];
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let inputIndex = 0;
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child.stdout?.on('data', (data) => {
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const output = data.toString();
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if (output.includes('?') && inputIndex < inputs.length) {
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child.stdin?.write(inputs[inputIndex] + '\n');
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inputIndex++;
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}
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});
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child.on('close', (code) => {
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expect(code).toBe(0);
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done();
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});
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});
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```
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### 9. Coverage-Driven Testing
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```typescript
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// Ensure all CLI commands are tested
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describe('CLI command coverage', () => {
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const commands = ['init', 'build', 'deploy', 'status', 'config'];
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commands.forEach((command) => {
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test(`${command} command exists`, () => {
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const { stdout } = runCLI('--help');
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expect(stdout).toContain(command);
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});
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test(`${command} has help text`, () => {
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const { stdout, code } = runCLI(`${command} --help`);
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expect(code).toBe(0);
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expect(stdout).toContain('Usage:');
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});
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});
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});
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```
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### 10. Performance Testing
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```typescript
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test('command executes within time limit', () => {
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const startTime = Date.now();
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const { code } = runCLI('status');
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const duration = Date.now() - startTime;
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expect(code).toBe(0);
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expect(duration).toBeLessThan(2000); // Should complete within 2 seconds
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});
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```
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## Best Practices
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1. **Use Test Fixtures**: Create reusable test data and cleanup functions
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2. **Mock External Dependencies**: Never make real API calls or database connections
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3. **Test Edge Cases**: Test boundary conditions, empty inputs, special characters
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4. **Async Handling**: Use proper async/await or promises for async operations
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5. **Cleanup**: Always cleanup temp files, reset mocks, restore environment
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6. **Isolation**: Tests should not depend on execution order
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7. **Clear Error Messages**: Write assertions with helpful failure messages
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## Common Advanced Patterns
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- Concurrent execution testing
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- File locking and race conditions
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- Signal handling (SIGTERM, SIGINT)
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- Large file processing
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- Streaming output
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- Progress indicators
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- Error recovery and retry logic
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## Resources
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- [Jest Advanced Features](https://jestjs.io/docs/advanced)
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- [Mocking with Jest](https://jestjs.io/docs/mock-functions)
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- [Snapshot Testing](https://jestjs.io/docs/snapshot-testing)
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