Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
git clone --depth 1 https://github.com/FeatureFactory-io/mimirWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/rules/featurefactory-io/mimir/do-test-first)<a href="https://agentmods.dev/rules/featurefactory-io/mimir/do-test-first"><img src="https://agentmods.dev/badge/rules/featurefactory-io/mimir/do-test-first/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/rules/featurefactory-io/mimir/do-test-first"><img src="https://agentmods.dev/badge/rules/featurefactory-io/mimir/do-test-first.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00000 | $0.00280 |
| Opus 5.5 | $0.00000 | $0.00112 |
| Sonnet 5.5 | $0.00000 | $0.00056 |
| Haiku 4.5 | $0.00000 | $0.00028 |
Grade A, and why
do-test-first scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 18d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
Tests prove behavior. You cannot claim a scenario, class, or method is implemented until tests pass.
- New code structure: follow playbook rule Skeletons First (
do-skeletons-first) (docstrings, types, stubs). - Write tests before implementation. Do not write tests whose only purpose is to hit
NotImplementedError—write assertions that should pass once real behavior exists. - Cover success (returns) and failure (
raises, errors, edge cases) for each unit of behavior. - If implementation contradicts docstring, ask the user which wins.
- Use
docs/features/to align scenarios with tests. - Order: method-level → API → integration. For integration, follow playbook rule Not Mock In Integration Tests (
do-not-mock-in-integration-tests). - Red–green: make the test fail, then implement until green.
- Use pytest; avoid mocks unless unavoidable.
Layout (never put tests in repo root):
| Kind | Path |
|---|---|
| Unit | tests/unit/ |
| Integration | tests/integration/ |
| API | tests/api/ |
| E2E | tests/e2e/ |
| Service | tests/services/ |
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 18d ago Changed e91d9b84d927
- 1mo ago First seen · 25 lines · 0 tokens per session scan A e93f7ef72dec
do-test-first is a cursor rule published in the GitHub repository FeatureFactory-io/mimir (16 stars, last pushed 17d ago), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 280 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other cursor rules, from other repositories
mcpnuke-tests
Test conventions for mcpnuke — enforces TDD workflow.
debug-issue
When the user reports a bug, an error, or unexpected behavior. Enforces four structured phases — reproduction, failing test, root cause isolation, fix and verify — to stop guess-and-check loops.
common-testing
Testing requirements: 80% coverage, TDD workflow.
testing_rules
A testing guide covering TDD, where tests are written before code, and BDD, where expected behavior is described in Given-When-Then form.
tdd
Test-driven development — red-green-refactor cycle.
testing-standards
testing guidelines and expectations.