Unit Testing

This skill should be used when editing Python code in the erk codebase. Use when writing, reviewing, or refactoring Python to ensure adherence to LBYL exception handling patterns, Python 3.13+ type syntax (list[str], str | None), pathlib operations, ABC-based interfaces, absolute imports, and explicit error boundaries at CLI level. Also provides production-tested code smell patterns from Dagster Labs for API design, parameter complexity, and code organization. Essential for maintaining erk's dignified Python standards.

Apply this repository's coding conventions and patterns. Use when writing or reviewing code in this codebase to ensure consistency with established patterns for DI, logging, error handling, testing, and documentation. Auto-trigger when implementing features, fixing bugs, or reviewing code changes.

Browser automation with Playwright for modern web scraping. Use this skill for scraping JavaScript-rendered pages, handling complex interactions, managing multiple browser contexts, or testing web applications. NOT needed for static HTML parsing or processing already-fetched content.

Comprehensive Storybook story creation guidelines. Covers story structure, naming conventions, and visual testing patterns. Reference this skill when creating Storybook stories for components with conditional rendering or complex UI states during Phase 2 (Testing & Stories).

Comprehensive React component coding guidelines, refactoring principles, and architectural patterns. **CRITICAL**: Focuses on patterns AI commonly fails to implement correctly, especially testability, props control, and component responsibility separation. Reference this skill when implementing or refactoring React components during Phase 2.

WebAssembly runtime execution and instantiation. Use when running compiled WebAssembly modules, testing WASM execution, or interfacing with WASM instances from Python.

QEMU ARM emulation for running ARM binaries and system images on x86 hosts. Use when emulating ARM architecture, running ARM Linux kernels, testing ARM binaries, or creating ARM development environments.

Algorithmic trading strategies and execution systems. Use for building trading bots, backtesting strategies, and implementing automated trading rules.

Implement Traveling Salesman Problem algorithms for route optimization. Use this skill when finding shortest routes through multiple points, solving pick path problems, implementing nearest neighbor or 2-opt algorithms, or optimizing travel sequences.

Rust testing patterns and best practices. Use this skill when writing, reviewing, or modifying Rust tests. Covers test organization, assertions with pretty_assertions, parameterized tests, and testing multiple input formats.

Unit testing framework for Python using pytest. Use when writing test cases, validating code behavior, checking test coverage, or debugging test failures.

Advanced scientific computing for portfolio optimization, statistical testing, and numerical methods. Use when minimizing portfolio variance, fitting distributions to returns data, performing correlation analysis, running hypothesis tests, or solving constrained optimization problems. Provides optimization algorithms (BFGS, SLSQP) and statistical distributions essential for risk modeling.

Graph algorithms for network analysis including shortest paths, cycle detection, and connectivity analysis. Create directed/undirected graphs with weighted edges. Use when modeling currency exchange networks, detecting arbitrage opportunities via negative cycles, finding optimal trading routes, calculating path lengths, analyzing network topology, or working with any connected data structures. Supports Bellman-Ford, Dijkstra, and other graph algorithms.

Comprehensive testing guidelines for Vitest and React Testing Library. Covers quality standards, AAA pattern, naming conventions, branch coverage, and best practices. Reference this skill when creating or updating test code during Phase 2 (Testing & Stories).

Strategic regression testing with test selection, impact analysis, and continuous regression management. Use when verifying fixes don't break existing functionality, planning regression suites, or optimizing test execution for faster feedback.

Regulatory compliance testing for GDPR, CCPA, HIPAA, SOC2, PCI-DSS and industry-specific regulations. Use when ensuring legal compliance, preparing for audits, or handling sensitive data.

Conduct context-driven code reviews focusing on quality, testability, and maintainability. Use when reviewing code, providing feedback, or establishing review practices.

Test application performance, scalability, and resilience. Use when planning load testing, stress testing, or optimizing system performance.

Cross-browser, cross-platform, and cross-device compatibility testing ensuring consistent experience across environments. Use when validating browser support, testing responsive design, or ensuring platform compatibility.

Advanced test reporting, quality dashboards, predictive analytics, trend analysis, and executive reporting for QE metrics. Use when communicating quality status, tracking trends, or making data-driven decisions.