---
name: rng-pool-sweep-blackbox-test
description: "Prove membership/absence in a randomly sampled pool (epithets-style) from black-box tests: prime-cycled Math.random sweeps every index; pool-first probe for setting precedence."
---

# Deterministic pool sweeps for random-sampling black-box tests

When a built bundle samples uniformly at random from a curated pool (epithet-style) and tests must prove a setting admits/excludes whole classes of pool entries, do NOT write probabilistic sampling tests. Two proven designs:

## 1. Full-pool sweep (class membership, distinct counts)

In the test driver (the process that imports the built bundle), before firing utterances:

```ts
let seed = 0;
Math.random = () => (seed++ % PRIME) / PRIME; // PRIME > pool size, e.g. 1009
```

The extension calls `Math.random()` at speak time, so the patch applies regardless of import order. Picks are `floor(random * poolSize)`; with N=PRIME samples the step is `< 1`, so **every index of every pool ≤ PRIME is visited exactly once**. Observable per-utterance text (e.g. the fixture server logs the synthesized `input=`) then reveals the entire sampling pool:

- distinct picks == pool size exactly (pin the total only if it is itself law);
- a sentinel name from class X appears / must never appear per mode — deterministic, zero flake;
- absence proofs are exhaustive, not lucky.

Drive one narration per iteration and gate the loop on the fixture's call counter advancing (`while (speechCount() < before + expected) await nap(2)`), otherwise typed/coalescing paths collapse iterations and counts drift.

**Wall-clock budget:** one sweep ≈ 20–40 s per pool; bats serializes and jobs cap at 600 s — run at most two sweeps per backgrounded bats `-f` selection, or launch full suites with `timeout: 0`.

## 2. Pool-first probe (setting precedence, milliseconds)

With the same patched RNG, the FIRST pick is `pool[0]`. Run each config mode with exactly one utterance and compare the first spoken name:

- mode-A setting vs env-mode-A → equal (settings key honored);
- env-X overriding file-Y → equals env-X's pick (precedence law);
- pick strings are pool literals that live in exactly one class (e.g. `comrade operator`).

Avoid: regex scans over spoken text (possessives/compounds false-fire), probabilistic "absent in 300 samples" tests (flake floor unless the block is contiguous), and reading source internals (white-box).

Red-first check: the sweep test for a not-yet-filtered pool must fail by SPEAKING the forbidden sentinel — if a "new mode" test passes pre-implementation, the probe accidentally tautologized (e.g. old pool[0] == new pool[0]); pick probe literals whose values differ between old and new behavior. Beware bats `setup()` rebuilding the bundle per test file: a long first sweep lets mid-session src edits leak into later tests' "red" proof — prove red from a pristine tree before implementing.