cli-testing-patterns

# CLI Testing Patterns

Comprehensive testing strategies for CLI applications using industry-standard testing frameworks. Covers command execution testing, exit code validation, output verification, interactive prompt testing, and integration testing patterns.

## Instructions

### When Testing Node.js CLI Tools

1. **Use Jest for testing CLI commands**
   - Import `child_process.execSync` for command execution
   - Create helper function to run CLI and capture output
   - Test exit codes, stdout, stderr separately
   - Handle both success and error cases

2. **Test Structure**
   - Set up CLI path relative to test location
   - Create `runCLI()` helper that returns `{stdout, stderr, code}`
   - Use try-catch to handle non-zero exit codes
   - Test common scenarios: version, help, unknown commands

3. **What to Test**
   - Command execution with various argument combinations
   - Exit code validation (0 for success, non-zero for errors)
   - Output content (stdout) validation
   - Error messages (stderr) validation
   - Configuration file handling
   - Interactive prompts (with mocked input)

### When Testing Python CLI Tools

1. **Use pytest with Click.testing.CliRunner**
   - Import `CliRunner` from `click.testing`
   - Create runner fixture for reusable test setup
   - Invoke commands with `runner.invoke(cli, ['args'])`
   - Check `result.exit_code` and `result.output`

2. **Test Structure**
   - Create pytest fixture for CliRunner instance
   - Use `runner.invoke()` to execute CLI commands
   - Access results through `result` object
   - Simulate interactive input with `input='responses\n'`

3. **What to Test**
   - Command invocation with various arguments
   - Exit code validation
   - Output content verification
   - Error handling and messages
   - Interactive prompt responses
   - Configuration handling

### Exit Code Testing Patterns

**Standard Exit Codes:**
- `0` - Success
- `1` - General error
- `2` - Misuse of command (invalid arguments)
- `126` - Comm