testing-strategy
Test selection strategy and scope guidance. Triggers: 'which tests should I run', 'test tiers', 'test marks', 'slow tests', 'integration vs unit', 'cross-module regression', 'test scope', 'what should I run', 'select tests', 'test batching'. NOT for: writing tests (use test-driven-development) or fixing broken tests (use fixing-tests).
Best use case
testing-strategy is best used when you need a repeatable AI agent workflow instead of a one-off prompt.
Test selection strategy and scope guidance. Triggers: 'which tests should I run', 'test tiers', 'test marks', 'slow tests', 'integration vs unit', 'cross-module regression', 'test scope', 'what should I run', 'select tests', 'test batching'. NOT for: writing tests (use test-driven-development) or fixing broken tests (use fixing-tests).
Teams using testing-strategy should expect a more consistent output, faster repeated execution, less prompt rewriting.
When to use this skill
- You want a reusable workflow that can be run more than once with consistent structure.
When not to use this skill
- You only need a quick one-off answer and do not need a reusable workflow.
- You cannot install or maintain the underlying files, dependencies, or repository context.
Installation
Claude Code / Cursor / Codex
Manual Installation
- Download SKILL.md from GitHub
- Place it in
.claude/skills/testing-strategy/SKILL.mdinside your project - Restart your AI agent — it will auto-discover the skill
How testing-strategy Compares
| Feature / Agent | testing-strategy | Standard Approach |
|---|---|---|
| Platform Support | Not specified | Limited / Varies |
| Context Awareness | High | Baseline |
| Installation Complexity | Unknown | N/A |
Frequently Asked Questions
What does this skill do?
Test selection strategy and scope guidance. Triggers: 'which tests should I run', 'test tiers', 'test marks', 'slow tests', 'integration vs unit', 'cross-module regression', 'test scope', 'what should I run', 'select tests', 'test batching'. NOT for: writing tests (use test-driven-development) or fixing broken tests (use fixing-tests).
Where can I find the source code?
You can find the source code on GitHub using the link provided at the top of the page.
SKILL.md Source
<analysis> Reference for choosing which tests to run based on change scope, and diagnosing cross-module regressions when targeted tests pass but the full suite fails. </analysis> <reflection> Did I match test scope to change scope, and did I avoid running the full suite when targeted tests would suffice? </reflection> # Testing Strategy ## Invariant Principles 1. **Scope Matches Change** - Test selection mirrors the scope of the code change; a single-file change does not justify a full suite run. 2. **Marks Are Proactive** - Tests are marked (slow, gpu, network) at authoring time based on what they require, not how fast they happen to run today. 3. **Full Suite Runs Once** - The complete test suite runs once per work unit completion, not after every incremental change. ## Test Tiers | Tier | Time | What | When | |------|------|------|------| | Unit | <1s each | Pure logic, no I/O, no external deps | After every change | | Integration | 1-5s each | Real resources (DB, filesystem, network) | After completing a logical unit of work | | E2E / Slow | >5s each | Full pipelines, large data, real services | Once per feature branch, before PR | ## Selecting What to Run - **Single file changed**: Run only the test file(s) that directly test that module. `src/auth/login.py` changed? Run `tests/test_login.py`. - **Shared dependency changed** (types, config, utilities): Grep for imports of the changed module across test files. Run all direct consumers. - **Multi-file task complete**: Run unit tests for all changed files in one command. - **All tasks in a work unit complete**: Run the full suite once. - **If >5 test files affected**: Run the full fast tier rather than listing individually. **Batching**: Write code for task 1, run targeted tests, write code for task 2, run targeted tests, run full suite once at end. ## Writing Tests for Speed Mock expensive resources in unit tests. Use smallest possible inputs. Never sleep in tests. One assertion focus per test. No fixtures heavier than the test itself. ## Test Marks Apply marks proactively when writing tests. A test that calls a GPU kernel is a GPU test even if it is fast today. | Mark | Meaning | |------|---------| | `slow` | >5 seconds. Skip during rapid iteration. | | `gpu`, `hardware` | Requires specific hardware. Skip on machines without it. | | `network` / `external` | Calls external services. Skip in offline/fast modes. | | `integration` | Requires multiple components working together. | | `smoke` | Minimal sanity checks. Run first. | If a project lacks marks, infer tiers from `--durations=0` (pytest) or equivalent: >5s is slow, >1s is integration, the rest are unit. ## Cross-Module Regression When the full suite fails after targeted tests passed: check failed test imports against your changed modules, then investigate shared mutable state, test ordering, or resource contention.
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