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pj
c76ba4b497
from().generate() draws from the picker's rng, which exists only inside walkActions. The model policy enumerates authored leaves outside that walk, so the sampler silently yielded its first item on every step: measured over 30 draws the seeded arm reached three targets in roughly equal proportion and the model was offered only the first. The two policies had different action spaces and nothing said so. A single-item sampler short-circuits before the rng, so both policies get the same value and it is not refused. Claude-Session: https://claude.ai/code/session_01A5KmftdEJ49A9z5mF5ESrX
sanderling
Autonomous property-based testing for mobile and web apps.
You write rules that must always hold about your app. sanderling explores the app on its own for minutes or hours, performing thousands of taps, swipes, and inputs, and records every step where a rule breaks. No scripted test paths. One TypeScript spec runs against Android, iOS, and web builds of the same app.
import { extract, always } from "@sanderling/spec";
import { defaultActions } from "@sanderling/spec/defaults";
import { noUncaughtExceptions } from "@sanderling/spec/defaults/properties";
const balance = extract("balance", s =>
parseInt(s.ax.find({ testTag: "Balance" })?.text ?? "0", 10));
export const properties = {
noUncaughtExceptions,
balanceNeverNegative: always(() => balance.current >= 0),
};
export const actionsRoot = defaultActions;
Every run produces a trace: one JSON line and one screenshot per step. sanderling replay opens it in a web UI for stepping through actions, screenshots, property timelines, and violations.
Alpha. Android, iOS, and web (Chrome driver only). Full scope in the v0.1.0 roadmap.
Docs
- Introduction: what property-based testing is and how sanderling works
- Case study: Folio: sanderling finding a real bug in a mobile app
- Getting started: install the CLI and run it against Folio
- Spec language reference
- Examples: folio (KMP, Android/iOS/web), folio-web (React + Vite)
- Architecture for contributors
sanderling, a wading bird that probes the shoreline for bugs that lie beneath.