Files
sanderling/pkg/spec
pj 05c8523762 fix(chrome): emit every markup attribute and read checked and selected off the property
the dump emitted a fixed standard attribute set, so a spec reading data-cents or data-account-id saw undefined on the goja host and nothing at all in the trace. it now keys every attribute by the name the markup writes, derived keys overwriting. checked and selected come from the dom property rather than whatever a component left on the object, which is also what the page-side element handle now reports, so a ticked box reads as ticked instead of reporting its starting state forever.
2026-08-16 17:44:04 +05:30
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@sanderling/spec

TypeScript spec API for sanderling, a property-based UI fuzzer for mobile and web apps.

Spec authors write properties (what the app must always or eventually do), extractors (structured state from the UI), and action generators (what sanderling is allowed to do). The sanderling CLI evaluates the spec in a loop against a running app.

Install

npm install --save-dev @sanderling/spec

Usage

import { extract, always, eventually, actions, weighted, taps, swipes, InputText, Tap } from "@sanderling/spec";

const loggedIn = extract((s) => !!s.ax.find("id:home-tab-bar"));
const balance = extract<number>((s) => (s.snapshots.balance as number) ?? 0);
const emailField = extract((s) => s.ax.find("id:email-field"));
const submitButton = extract((s) => s.ax.find("id:sign-in-button"));

export const properties = {
  balanceNeverNegative: always(() => balance.current >= 0),
  loginSucceeds: eventually(() => loggedIn.current).within(30, "seconds"),
};

const doLogin = actions(() => {
  if (loggedIn.current) return [];
  const email = emailField.current;
  const submit = submitButton.current;
  if (!email || !submit) return [];
  return [InputText({ into: email, text: "[email protected]" }), Tap({ on: submit })];
});

export const actionsRoot = weighted(
  [50, doLogin],
  [10, taps],
  [2,  swipes],
);

Setup actions

Some action generators are not fuzz targets but preconditions: they drive the app from a fresh state into the surface you actually want to fuzz (login, onboarding, permission grants, seed data). Export them as setup instead of mixing them into actionsRoot. The runner tries setup first; if it yields no action, it falls through to actionsRoot. State regressing back across the precondition (e.g. logout under fuzz) automatically re-engages setup.

const login = actions(() => {
  if (loggedIn.current) return [];
  return [InputText({ into: emailField.current!, text: "[email protected]" }), Tap({ on: submitButton.current! })];
});

export const setup = login;
export const actionsRoot = weighted([60, browse], [40, edit]);

(globalThis as { setup?: unknown }).setup = setup;

Setup is just an ActionGenerator; compose with actions, weighted, or whenRoute exactly like the main pool.

Works identically across Android, iOS, and web targets.