Unit Testing

Generate realistic, consistent test data using factories, fixtures, and fake data libraries. Use for test data, fixtures, mock data, faker, test builders, and seed data generation.

Evaluate test suite quality by introducing code mutations and verifying tests catch them. Use for mutation testing, test quality, mutant detection, Stryker, PITest, and test effectiveness analysis.

Flaky test fix pattern - replaces arbitrary timeouts with condition pollingthat waits for actual state changes.

Expert guidance for Dagster data orchestration including assets, resources, schedules, sensors, partitions, testing, and ETL patterns. Use when building or extending Dagster projects, writing assets, configuring automation, or integrating with dbt/dlt/Sling.

Skill testing methodology - run scenarios without skill (RED), observe failures,write skill (GREEN), close loopholes (REFACTOR).

Four-phase debugging framework - root cause investigation, pattern analysis,hypothesis testing, implementation. Ensures understanding before attempting fixes.

Design and implement integration tests that verify component interactions, API endpoints, database operations, and external service communication. Use for integration test, API test, end-to-end component testing, and service layer validation.

Manage monorepo architectures using Lerna, Turborepo, and Nx. Configure workspaces, dependency versioning, and cross-package testing.

Structured workflow for disaster recovery planning, implementation, and testingincluding RTO/RPO definition, DR strategy selection, and failover procedures.

Gate 2 sub-skill - validates uncertain mappings from Gate 1 and confirmsall field specifications through testing.

Handle cross-platform compatibility including file paths, environment detection, platform-specific dependencies, and testing across Windows, macOS, and Linux. Use when dealing with platform-specific code or OS compatibility.

Test quality guard - prevents testing mock behavior, production pollution withtest-only methods, and mocking without understanding dependencies.

Write comprehensive unit tests with high coverage using testing frameworks like Jest, pytest, JUnit, or RSpec. Use when writing tests for functions, classes, components, or establishing testing standards.

Implement synthetic monitoring and automated testing to simulate user behavior and detect issues before users. Use when creating end-to-end test scenarios, monitoring API flows, or validating user workflows.

TDD for process documentation - write test cases (pressure scenarios), watchbaseline fail, write skill, iterate until bulletproof against rationalization.

Migrate Express.js REST APIs to Fastify with automated testing, performance benchmarking, and schema generation. Use when migrating Express applications to Fastify, modernizing Node.js APIs, improving API performance, or when users mention Express to Fastify migration, Fastify conversion, API modernization, or performance optimization of Express apps.

Design and implement CI/CD pipelines with GitHub Actions, GitLab CI, Jenkins, or CircleCI. Use for automated testing, building, and deployment workflows.

Measure relationships between variables using correlation coefficients, correlation matrices, and association tests for correlation measurement, relationship analysis, and multicollinearity detection

Agent testing methodology - run agents with test inputs, observe outputs,iterate until outputs are accurate and well-structured.

Test system behavior under extreme load conditions to identify breaking points, capacity limits, and failure modes. Use for stress test, capacity testing, breaking point analysis, spike test, and system limits validation.