cli-testing-patterns_skill

Overview

This skill packages battle-tested CLI testing strategies for Node.js (Jest) and Python (pytest + Click.testing.CliRunner). It focuses on command execution, exit-code validation, output and error verification, interactive prompt simulation, and integration testing patterns for professional CLI tooling.

How this skill works

The skill describes concrete test structures and helper patterns: a runCLI helper using child_process.execSync for Jest, and a pytest fixture that yields CliRunner for Click-based CLIs. It explains how to invoke commands, capture stdout/stderr, assert exit codes, and simulate interactive input. It also includes templates, test utilities, and scripts to scaffold test suites and CI-friendly execution.

When to use it

• Writing or reviewing tests for Node.js CLIs (Jest) or Python Click/Typer CLIs (pytest + CliRunner)
• Validating command execution, exit codes, and CLI output formats
• Implementing interactive prompt tests or providing mocked stdin
• Building integration test suites that exercise multi-command workflows
• Enforcing consistent CLI testing patterns across a team or CI pipeline

Best practices

• Test both success (0) and failure (non-zero) exit codes, and verify specific codes for error classes
• Isolate tests: use fixtures and mocks to avoid real network calls or file-system side effects
• Use helper functions (runCLI, runner fixtures) to keep tests concise and consistent
• Assert output flexibly (substring checks) and precisely for structured formats (JSON/YAML)
• Keep CLI tests fast; reserve slow end-to-end integration tests for separate suites

Example use cases

• Unit tests asserting --version and --help return exit code 0 and expected text
• Jest suites that capture stdout/stderr and verify error messages and exit codes for invalid args
• pytest tests using CliRunner.invoke to simulate user input for interactive prompts
• Integration tests that run multi-command workflows and validate state transitions and outputs
• CI pipelines that run run-cli-tests.sh and fail on coverage regressions