test-expert_skill

Overview

This skill helps developers design and implement effective tests, adopt test-driven development (TDD), and raise test quality across unit, integration, and end-to-end levels. I focus on practical patterns, tooling tips for Python (pytest) and other ecosystems, and measurable coverage goals to keep your project safe to change. Use this skill to build reliable, fast, and maintainable test suites.

How this skill works

I inspect code layout, testing targets, and current test practices, then recommend concrete tests, fixtures, and CI steps. I guide you through the Red-Green-Refactor TDD loop, suggest what to mock or stub, and translate testing principles into examples and test names. I also provide coverage goals, test organization patterns, and CI configuration snippets to integrate tests into your workflow.

When to use it

• You need to write tests for new or existing code
• You want to adopt or improve TDD practices
• You need higher confidence before refactoring critical logic
• You want to design stable integration or E2E tests
• You want actionable guidance for pytest, mocking, or CI pipelines

Best practices

• Follow the Test Pyramid: many unit tests, some integration, few E2E
• Write tests first where feasible; use Red-Green-Refactor
• Keep tests FAST, ISOLATED, and SELF-VALIDATING (FIRST)
• Use AAA (Arrange, Act, Assert) and descriptive test names
• Mock external services, seed random data, and avoid flakiness
• Aim for 80%+ coverage overall; 100% for critical paths only

Example use cases

• Create unit tests and parameterized cases for a Calculator class using pytest
• Design integration tests that exercise database persistence with setup/teardown fixtures
• Implement TDD for a new API endpoint: write failing tests, implement minimal code, then refactor
• Replace slow external calls with mocks in unit tests and write one integration test against a test database
• Add CI steps to run pytest with coverage and upload reports to a coverage service