feedBack/tests/js/highway_3d_arp_deferral.test.js

// Pins the arpeggio chord-gem deferral gating in plugins/highway_3d/screen.js
// (feedBack#262). Without these guards, an over-eager `deferChordGems` makes
// arpeggio frames empty when standalone notes don't actually cover the shape,
// and an under-eager one duplicates gems on top of the standalone passage.
//
// Source-level only — same strategy as the other tests/js/ files.

const { test } = require('node:test');
const assert = require('node:assert/strict');
const fs = require('node:fs');
const path = require('node:path');

const SCREEN_JS = path.join(__dirname, '..', '..', 'plugins', 'highway_3d', 'screen.js');

test('chordShapeCoveredByStandaloneNotes helper exists with the expected signature', () => {
    const src = fs.readFileSync(SCREEN_JS, 'utf8');
    assert.match(
        src,
        /function\s+chordShapeCoveredByStandaloneNotes\s*\(\s*ch\s*,\s*shape\s*,\s*notesArr\s*,\s*timeWin\s*\)/,
        'helper that scans the note stream for shape coverage must remain on screen.js',
    );
});

test('deferChordGems gates both synth and explicit+covered branches on note-stream coverage', () => {
    // Either branch firing without coverage produces the empty-lavender-frame
    // regression PR #262 fixed. Pin both predicates so a refactor that drops
    // one gate fails the test.
    const src = fs.readFileSync(SCREEN_JS, 'utf8');
    assert.match(
        src,
        /const\s+deferChordGems\s*=\s*\(\s*ch\.h3dSynth\s*&&\s*noteStreamCoversArpShape\(\)\s*\)\s*\|\|\s*inferredArpPattern\s*\|\|\s*\(\s*hsHintFrame\.explicit\s*&&\s*hsHintFrame\.covered\s*&&\s*noteStreamCoversArpShape\(\)\s*\)/,
        'deferChordGems must guard the h3dSynth and explicit+covered branches with the coverage check',
    );
});

test('noteStreamCoversArpShape is computed lazily (called, not eagerly bound)', () => {
    // Eager allocation regressed perf on dense charts (Copilot review on PR
    // #262). The shape must be a callable so short-circuit evaluation skips
    // the note-stream scan when neither gating branch needs it.
    const src = fs.readFileSync(SCREEN_JS, 'utf8');
    assert.match(
        src,
        /const\s+noteStreamCoversArpShape\s*=\s*(?:\(\s*\)\s*=>|function(?:\s+\w+)?\s*\(\s*\))/,
        'noteStreamCoversArpShape must be an arrow/function so the scan is lazy',
    );
    assert.doesNotMatch(
        src,
        /const\s+noteStreamCoversArpShape\s*=\s*chordShapeCoveredByStandaloneNotes\(/,
        'noteStreamCoversArpShape must not eagerly invoke the coverage helper',
    );
});