pj
45b7624280
json has no undefined, so an extractor whose getter returned one had its
whole index dropped by JSON.stringify. that index then kept goja's
dump-derived value while its neighbours held the page's, and a property
comparing previous to current across the split fires on a healthy app.
folio has nine on(route, tag) extractors, so this was most extractors on
most steps.
each reading is wrapped in a {value} envelope: the drop now happens
inside the entry, and an absent value means the getter returned
undefined, which is what the goja host records for the same getter. a
json null would instead claim it returned null and x.current ===
undefined would answer differently on the two hosts.
@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.