zebra-report/test/video-track-removal.test.js

#!/usr/bin/env node
/* watchVideoTrackForRemoval state-machine tests.
 *
 *     node test/video-track-removal.test.js
 *
 * The function is the receive-side stream lifecycle in zebra-spaces.html
 * — it watches a remote MediaStreamTrack and removes the tile when the
 * publisher GENUINELY stops sharing (a real unshare or a leave). It must
 * NOT remove the tile on transient mutes (NACK retransmission gap,
 * network blip, CPU pressure on publisher, mobile network handoff).
 *
 * The shipped function has three legitimate teardown paths:
 *   - track 'ended'  -> publisher closed PC or SFU renegotiated away
 *                       (peer left, screen-share window closed, etc.)
 *   - sustained mute -> RTP stopped for >VIDEO_REMOVE_MUTE_WINDOW_MS
 *                       (publisher unshared without a clean close)
 *   - initial mute (before any unmute) -> NEVER removes (fresh remote
 *                       tracks start muted until first packet arrives)
 *
 * Tests run on the real shipped code: we extract the function out of
 * zebra-spaces.html, inject a fake setTimeout/clearTimeout for time
 * control, and drive synthetic event sequences. */

const fs = require('fs');
const path = require('path');
const src = fs.readFileSync(path.join(__dirname, '..', 'web', 'zebra-spaces.html'), 'utf8');

/* lift a top-level function literal out of zebra-spaces.html by locating
 * its head, then brace-matching to the closing }. */
function extract(re){
  const m = src.match(re);
  if (!m) throw new Error('could not find ' + re + ' in zebra-spaces.html');
  let i = src.indexOf('{', m.index + m[0].length), depth = 0, j = i;
  for (; j < src.length; j++){
    if (src[j] === '{') depth++;
    else if (src[j] === '}') { if (--depth === 0) { j++; break; } }
  }
  return src.slice(m.index, j);
}

const watchSrc = extract(/function watchVideoTrackForRemoval\(/);

/* Shipped constants. Read from source so the tests always validate
 * what's actually live — if either window changes the assertions below
 * catch an accidental shorten. */
const winM = src.match(/const\s+VIDEO_REMOVE_MUTE_WINDOW_MS\s*=\s*(\d+)\s*;/);
if (!winM) throw new Error('VIDEO_REMOVE_MUTE_WINDOW_MS not found in source');
const SHIPPED_WINDOW_MS = parseInt(winM[1], 10);

const winScreenM = src.match(/const\s+VIDEO_REMOVE_MUTE_WINDOW_SCREEN_MS\s*=\s*(\d+)\s*;/);
if (!winScreenM) throw new Error('VIDEO_REMOVE_MUTE_WINDOW_SCREEN_MS not found in source');
const SHIPPED_WINDOW_SCREEN_MS = parseInt(winScreenM[1], 10);

/* ============================ fake clock ============================ */
let fakeNow = 0;
let pending = new Map();   // id -> { fireAt, fn }
let nextTimerId = 1;
function fakeSetTimeout(fn, ms){
  const id = nextTimerId++;
  pending.set(id, { fireAt: fakeNow + ms, fn });
  return id;
}
function fakeClearTimeout(id){ pending.delete(id); }
function advance(ms){
  fakeNow += ms;
  /* fire any timers whose fireAt has elapsed, in deadline order */
  const ready = [...pending.entries()]
    .filter(([, t]) => t.fireAt <= fakeNow)
    .sort((a, b) => a[1].fireAt - b[1].fireAt);
  for (const [id, t] of ready){
    pending.delete(id);
    t.fn();
  }
}
function resetClock(){
  fakeNow = 0;
  pending = new Map();
  nextTimerId = 1;
}

/* logLine stub — captures so we can assert on diagnostic output. */
let logs = [];
function logLine(kind, msg){ logs.push({ kind, msg }); }
function resetLogs(){ logs = []; }

/* harness — Function-constructor scope so the function's free
 * references resolve to our fakes, not the host's real globals. */
const harness = new Function(
  'setTimeout', 'clearTimeout', 'logLine',
  'VIDEO_REMOVE_MUTE_WINDOW_MS', 'VIDEO_REMOVE_MUTE_WINDOW_SCREEN_MS',
  watchSrc + '\nreturn watchVideoTrackForRemoval;'
);
const watchVideoTrackForRemoval = harness(
  fakeSetTimeout, fakeClearTimeout, logLine,
  SHIPPED_WINDOW_MS, SHIPPED_WINDOW_SCREEN_MS,
);

/* ============================ fake track ============================ */
function makeTrack(){
  const listeners = {};
  let muted = true; // remote tracks start muted (matches MediaStreamTrack on creation)
  return {
    get muted(){ return muted; },
    setMuted(v){ muted = v; },
    addEventListener(evt, fn){
      (listeners[evt] = listeners[evt] || []).push(fn);
    },
    fire(evt){
      for (const fn of (listeners[evt] || [])) fn();
    },
  };
}

/* ============================ test harness ============================ */
let pass = 0, fail = 0;
function test(name, fn){
  resetClock();
  resetLogs();
  try { fn(); console.log('  ✓ ' + name); pass++; }
  catch (e){ console.log('  ✗ ' + name + ' — ' + (e.message || e)); fail++; }
}
function eq(a, b, msg){
  if (a !== b) throw new Error((msg || 'expected') + ' — got ' + JSON.stringify(a) + ' want ' + JSON.stringify(b));
}
function truthy(v, msg){ if (!v) throw new Error(msg || 'expected truthy'); }
function falsy(v, msg){ if (v) throw new Error(msg || 'expected falsy'); }

/* ====================== unit: state-machine transitions ====================== */

console.log('watchVideoTrackForRemoval unit:');

test('shipped mute-window is at least 10s — anything less is too aggressive', () => {
  truthy(SHIPPED_WINDOW_MS >= 10000, 'window ' + SHIPPED_WINDOW_MS + ' < 10000');
});

test('shipped screen-window is at least 60s — static screens stay quiet', () => {
  truthy(SHIPPED_WINDOW_SCREEN_MS >= 60000,
    'screen window ' + SHIPPED_WINDOW_SCREEN_MS + ' < 60000');
  truthy(SHIPPED_WINDOW_SCREEN_MS > SHIPPED_WINDOW_MS,
    'screen window must be longer than camera window');
});

test('callers can override the window per-kind (screen window honored)', () => {
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++, SHIPPED_WINDOW_SCREEN_MS);
  t.setMuted(false); t.fire('unmute');
  t.setMuted(true);  t.fire('mute');
  /* the camera window has passed — but we passed the screen window, so
   * the tile must survive */
  advance(SHIPPED_WINDOW_MS + 1000);
  eq(removed, 0, 'camera-window elapsed but screen-window in effect — must not remove');
  /* still inside the screen window */
  advance(SHIPPED_WINDOW_SCREEN_MS - SHIPPED_WINDOW_MS - 2000);
  eq(removed, 0, 'still inside screen window');
  /* now we cross the screen window */
  advance(2000);
  eq(removed, 1, 'screen window elapsed — removed');
});

test('invalid window argument falls back to camera default', () => {
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++, 'not a number');
  t.setMuted(false); t.fire('unmute');
  t.setMuted(true);  t.fire('mute');
  advance(SHIPPED_WINDOW_MS + 100);
  eq(removed, 1, 'bad windowMs should fall back to default, not disable removal');
});

test('initial mute (never flowed) does NOT schedule a removal', () => {
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++);
  t.setMuted(true);
  t.fire('mute');             // fresh remote-track mute
  advance(60000);             // way past any reasonable timeout
  eq(removed, 0, 'initial-mute should never remove');
  eq(pending.size, 0, 'no timer should have been armed');
});

test('flowing + sustained mute past window removes', () => {
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++);
  t.setMuted(false); t.fire('unmute');         // RTP started
  t.setMuted(true);  t.fire('mute');            // RTP stopped
  advance(SHIPPED_WINDOW_MS - 1);
  eq(removed, 0, 'should NOT fire before the window elapses');
  advance(2);
  eq(removed, 1, 'should fire exactly once at window');
});

test('flowing + brief mute + unmute cancels the removal', () => {
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++);
  t.setMuted(false); t.fire('unmute');
  t.setMuted(true);  t.fire('mute');
  advance(SHIPPED_WINDOW_MS - 1000);            // just under window
  t.setMuted(false); t.fire('unmute');          // RTP resumed in time
  advance(60000);                               // wait way past — nothing
  eq(removed, 0);
});

test('ended event removes immediately and cancels any pending timer', () => {
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++);
  t.setMuted(false); t.fire('unmute');
  t.setMuted(true);  t.fire('mute');             // timer armed
  truthy(pending.size > 0, 'expected a pending timer');
  t.fire('ended');
  eq(removed, 1, 'ended should remove once');
  eq(pending.size, 0, 'ended must cancel the mute timer');
  advance(60000);
  eq(removed, 1, 'no further calls after ended');
});

test('removeFn is idempotent — never called twice', () => {
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++);
  t.setMuted(false); t.fire('unmute');
  t.setMuted(true);  t.fire('mute');
  advance(SHIPPED_WINDOW_MS + 100);             // first removal
  eq(removed, 1);
  t.fire('ended');                              // second teardown signal
  eq(removed, 1, 'still 1 — already removed');
  t.fire('mute'); advance(SHIPPED_WINDOW_MS);
  eq(removed, 1);
});

test('redundant mute events do not start a second timer', () => {
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++);
  t.setMuted(false); t.fire('unmute');
  t.setMuted(true);
  t.fire('mute');
  const firstSize = pending.size;
  t.fire('mute'); t.fire('mute');
  eq(pending.size, firstSize, 'extra mute events should be no-ops while a timer is pending');
});

test('rescue log line fires when unmute saves the tile', () => {
  const t = makeTrack();
  watchVideoTrackForRemoval(t, () => {});
  t.setMuted(false); t.fire('unmute');
  t.setMuted(true);  t.fire('mute');             // timer armed
  t.setMuted(false); t.fire('unmute');           // saved!
  const rescue = logs.find(l => /RTP resumed/.test(l.msg));
  truthy(rescue, 'expected an RTP-resumed log line after rescue');
});

test('removal log line fires when the timeout takes the tile', () => {
  const t = makeTrack();
  watchVideoTrackForRemoval(t, () => {});
  t.setMuted(false); t.fire('unmute');
  t.setMuted(true);  t.fire('mute');
  advance(SHIPPED_WINDOW_MS + 100);
  const remove = logs.find(l => /muted >/.test(l.msg) && /removing tile/.test(l.msg));
  truthy(remove, 'expected a removal log line after timeout');
});

test('mute-then-unmute-before-mute-fires-after-unmute keeps tile alive', () => {
  /* this is the rapid oscillation case: NACK retransmission gap may
   * fire mute then unmute many times within a single second. None of
   * those should trigger removal as long as unmute lands before the
   * window expires. */
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++);
  t.setMuted(false); t.fire('unmute');
  for (let i = 0; i < 5; i++){
    t.setMuted(true);  t.fire('mute');
    advance(100);
    t.setMuted(false); t.fire('unmute');
    advance(100);
  }
  advance(60000);
  eq(removed, 0, 'oscillation under window should never remove');
});

/* ====================== integration: realistic lifecycles ====================== */

console.log('watchVideoTrackForRemoval integration:');

test('lifecycle: fresh track -> flow -> publisher unshares -> tile removed', () => {
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++);
  /* fresh remote track: arrives muted, no immediate removal */
  t.setMuted(true); t.fire('mute');
  advance(2000);
  eq(removed, 0);
  /* RTP starts */
  t.setMuted(false); t.fire('unmute');
  advance(30000);  // happy stream for 30s
  eq(removed, 0);
  /* publisher unshares — SFU stops the transceiver — RTP halts */
  t.setMuted(true); t.fire('mute');
  advance(SHIPPED_WINDOW_MS - 1);
  eq(removed, 0, 'should still be deciding');
  advance(2);
  eq(removed, 1, 'cleaned up after window');
});

test('lifecycle: mobile network handoff (long mute) recovers without removal', () => {
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++);
  t.setMuted(false); t.fire('unmute');
  t.setMuted(true);  t.fire('mute');
  /* handoff stalls RTP for almost the full window */
  advance(SHIPPED_WINDOW_MS - 500);
  /* signal restores just in time */
  t.setMuted(false); t.fire('unmute');
  advance(60000);
  eq(removed, 0, 'handoff that recovers under window must not remove');
});

test('lifecycle: peer leaves abruptly -> ended fires -> tile removed once', () => {
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++);
  t.setMuted(false); t.fire('unmute');
  advance(5000);
  t.fire('ended');                              // SFU renegotiated the track away
  eq(removed, 1);
});

test('lifecycle: hard refresh of publisher (same pubkey) -> brief gap -> new track restored', () => {
  /* this is the cascade fox flagged: on a hard refresh the publisher
   * page reconnects, the SFU supplants the stale publisher, the
   * SUBSCRIBER's existing track briefly mutes during the SSE
   * renegotiation churn. Must not remove. */
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++);
  t.setMuted(false); t.fire('unmute');
  advance(2000);
  /* renegotiation gap: mute fires while SFU swaps the source */
  t.setMuted(true); t.fire('mute');
  advance(800);                                 // typical renegotiation latency
  t.setMuted(false); t.fire('unmute');
  advance(30000);
  eq(removed, 0, 'renegotiation blip must not look like an unshare');
});

test('lifecycle: publisher process crashes -> mute holds -> tile removed at window', () => {
  const t = makeTrack();
  let removed = 0;
  watchVideoTrackForRemoval(t, () => removed++);
  t.setMuted(false); t.fire('unmute');
  advance(10000);
  /* publisher's PC dies but the SFU hasn't yet detected ICE failure
   * — track stays muted from the subscriber's perspective until the
   * SFU eventually renegotiates. Window catches it. */
  t.setMuted(true); t.fire('mute');
  advance(SHIPPED_WINDOW_MS + 100);
  eq(removed, 1);
});

/* ============================== summary ============================== */

console.log('\n' + pass + ' passed, ' + fail + ' failed');
process.exit(fail === 0 ? 0 : 1);