selectools-testing

A collection of testing rules for the Selectools codebase, covering test locations, fake service providers, call recording, and regression tests.

In plain words
What is it for?
It guides unit, integration, provider, agent, retrieval, tool, and regression tests, including how to build test doubles and where to place them.
Why use it?
It makes tests consistent and helps prevent bugs such as providers silently receiving the wrong arguments.

Cursor rule for Cursor

Install

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.

agentmods
npx agentmods add rules/johnnichev/selectools/selectools-testing
Clone the repo
git clone --depth 1 https://github.com/johnnichev/selectools

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 466 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.00466
Opus 5 $0.00000 $0.00233
Sonnet 5 $0.00000 $0.00093
Haiku 4.5 $0.00000 $0.00047

Measured yesterday against content hash 451cd6583b5f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

selectools-testing 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 yesterday.

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.

.cursor/rules/selectools-testing.mdc · 59 lines

What it actually says

Testing Rules

Test Organization

  • tests/test_<module>.py — unit tests for each source module
  • tests/agent/ — agent core, observer, batch, regression tests
  • tests/providers/ — provider-specific, model registry, streaming, format tests
  • tests/rag/ — RAG pipeline, chunking, hybrid search, vector store tests
  • tests/integration/ — cross-module integration tests
  • tests/tools/ — tool system tests

Mock Provider Pattern

class FakeProvider:
    name = "fake"
    supports_streaming = True
    supports_async = True

    def complete(self, *, model, system_prompt, messages, tools=None, **kw):
        return Message(role=Role.ASSISTANT, content="response")

Always include tools=None in signature — missing it silently hides bugs.

Recording Provider Pattern

Use to verify exact args passed to provider methods:

class RecordingProvider(FakeProvider):
    def __init__(self):
        self.calls = []
    def complete(self, **kwargs):
        self.calls.append(("complete", kwargs))
        return Message(role=Role.ASSISTANT, content="ok")

Regression Tests

  • Go in tests/agent/test_regression.py
  • Each test class documents the specific bug it prevents
  • Name pattern: TestXxxHandling describing the failure mode
  • Include a docstring explaining what broke and when

Assertions

  • Model counts: update when adding/removing models
  • Observer events: verify run_id is passed to all events
  • Streaming: verify ToolCall objects are yielded (not strings)
  • Policy: verify deny actually blocks execution
  • Guardrails: verify block raises, rewrite modifies content

Running Tests

pytest tests/ -x -q                 # All tests, stop on first failure
pytest tests/ -k "not e2e" -x -q    # Skip E2E (CI mode)
pytest tests/agent/ -x -q           # Just agent tests
Changes

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.

  1. yesterday First seen · 59 lines · 0 tokens per session scan A 451cd6583b5f

Subscribe to this mod's changes

selectools-testing is a cursor rule published in the GitHub repository johnnichev/selectools (11 stars, last pushed 1mo ago), licensed Apache-2.0. It costs nothing until one of its globs matches a file; then it loads 466 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.