`compile()` for tests

busk() only accepts steps — one script, one clock. Mock UI updates belong in { run } steps or click handlers, not parallel schedules on the routine.

compile() runs the same timeline math as busk() without mounting a show. You use it to assert glide times, loop length, and when { run } steps fire.

What you pass in

1. steps — the routine script (Step shapes).
2. resolveTarget — your ResolveTarget callback. Busker does not ship a default for tests; you decide where selectors “are” in px.
3. motion (optional) — usually DEFAULT_MOTION in app code, or a fixed config in tests so distances map to predictable ms.
4. start (optional) — cursor start in px, default [0, 0]. (On a live routine, start is a fraction of the root; busk() converts that to px before compiling.)

Example

Stub selectors to fixed positions so assertions stay stable:

typescript

import {compile} from '@logfox/busker';
import type {Point} from '@logfox/busker';

const resolveTarget = (to: string | Point, from: Point): Point | null => {
    if (Array.isArray(to)) {
        // Fractions → px the same way as a 100×100 root in tests
        return [to[0] * 100, to[1] * 100];
    }
    if (to === '#save') return [200, 40];
    if (to === '#cancel') return [280, 40];

    return from;
};

const fixedMotion = {pxPerSecond: 1e9, minMoveMs: 100, dwellMs: 50};

const {glides, duration, runs} = compile(
    [{wait: 100}, {click: '#save'}, {wait: 200}, {run: () => {}}, {click: '#cancel'}],
    resolveTarget,
    fixedMotion,
    [0, 0],
);

// glides[0] → { to: '#save', from: 100, until: 200, press: 250 }
// runs[0].at → 650 (after wait, click beat, and wait: 200)
// duration → 1520 (includes ring after last click)

Return shape and field types: Glide, ScheduledRun, and compile() in the API reference.

Tips

• Match motion to what you care about: real DEFAULT_MOTION for integration-style checks, exaggerated pxPerSecond / minMoveMs in unit tests for round numbers.
• Return null from resolveTarget when an element is hidden; compile uses a short glide. At runtime, busk() can remeasure and call stretchGlide() — see timeline.spec.ts in the repo.
• Need when each step starts (not just glides and runs)? Use compileStepStarts().

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