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test-architecture-strategy

Testing & Quality
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Design a sustainable test architecture using test desiderata, test pyramid tradeoffs, fast and slow test separation, integration boundaries, CI feedback loops, and architecture choices that make code testable. Use when a test suite is too slow, too brittle, too mock-heavy, unclear about unit vs integration coverage, or needs a testing strategy before major growth.

QUICK START

How to use this skill

Bring this guide into your coding agent with a prompt tailored to the tool you use.

  1. Open your project in Codex.
  2. Copy the prompt below and paste it into your agent.
  3. Review the proposed files and risks before you approve installation.
Prompt to paste
I want to install this Agent Skill for this project in Codex.

Source SKILL.md: https://github.com/hashgraph-online/awesome-codex-plugins/blob/HEAD/plugins/LVTD-LLC/skills/skills/test-architecture-strategy/SKILL.md

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First, summarize what it does, its dependencies, license status if identifiable, and any risks. Show the exact files you propose to add under .agents/skills/test-architecture-strategy/. Do not write files or run scripts until I approve.

After I approve, install the complete skill folder, including required referenced files, into that project location. Verify it is discoverable, then tell me its actual invocation name and how to use it. Do not claim it is installed until you have verified it.

Copying this prompt does not install or run the skill. Review third-party files before use. Codex skill guide

Test Architecture Strategy

Use this skill to reason about the shape of a test suite, not one test at a time. The goal is a suite that gives confidence, runs quickly enough for flow, and still catches integration failures at important boundaries.

Source Traceability

Primary source: Harry Percival, Test-Driven Development with Python, 3rd ed. Guidance is transformed and paraphrased from chapter 27 and Appendix A, especially test desiderata, fast/slow test tradeoffs, test pyramid thinking, boundaries, ports and adapters, functional core/imperative shell, and when to rethink architecture.

Workflow

  1. Inventory the current suite.

    • Identify unit, integration, functional/end-to-end, smoke, and manual checks.
    • Capture runtime, flake rate, CI split, and developer feedback path.

  2. Classify the pain.

    • Slow feedback.
    • Brittle structure-coupled tests.
    • Mock-heavy tests with low confidence.
    • Missing boundary coverage.
    • Too many end-to-end tests.

  3. Choose the target shape.

    • Fast tests for core logic and detailed cases.
    • Integration tests at real boundaries.
    • A small number of end-to-end tests for critical journeys.
    • Production monitoring or smoke checks where tests are not enough.

  4. Move one slice at a time.

    • Extract pure logic or service boundaries.
    • Replace exhaustive end-to-end coverage with lower-level tests plus one journey.
    • Add contract or integration checks for external systems.
    • Define a runtime red line before the suite becomes painful.

Read test-architecture-patterns.md for audit questions, migration patterns, and decision tables.

Decision Rules

  • If tests are slow but valuable, first separate fast local feedback from full CI proof.
  • If unit tests require databases or frameworks everywhere, identify pure core logic that can move inward.
  • If mocks dominate, use architecture seams rather than more mocks.
  • If end-to-end tests cover many detailed branches, demote detailed cases to lower-level tests.
  • If integration bugs keep escaping, add boundary tests before deleting broad coverage.

Guardrails

  • Do not chase a textbook test pyramid without respecting the product's real risks.
  • Do not delete slow tests until replacement confidence exists.
  • Do not make every piece of code "pure" at the cost of framework clarity.
  • Do not optimize runtime without measuring.

Verification

Before finishing, produce:

  • Current suite map.
  • Pain classification with evidence.
  • Target suite shape.
  • First migration slice.
  • Verification commands or metrics that prove progress.