@pytest.mark.slow
    def test_in_flight_poll_does_not_overwrite_stepped_day():
        """PART 3 behavioural test: an in-flight poll tick between the click and load()'s response
        must NOT call load(curDay) — otherwise the AbortController aborts the in-flight stepped-day
        fetch and the page snaps back to today.
    
        The harness DELIBERATELY makes load() take 50ms so the race window between the click and
        load()'s response is wide open (>= 4 poll ticks). With the PART 3 fix
        (`!_twNavPinned` inside the setInterval callback's predicate), the in-flight poll skips
        because the click set `_twNavPinned=true` BEFORE the load() resolved.
    
        Asserts AFTER a 100ms wait — so a test that asserts immediately after the click would
        pass on a broken build while the operator still sees the page snap back. That trap has
        now caught this bug twice (night-watch's two rounds); the test deliberately waits so the
        race window fully closes before the assertion.
        """
        import shutil
        import subprocess
        import tempfile
    
        node_bin = shutil.which("node")
        if not node_bin:
            pytest.skip("node not available on this box")
        with tempfile.NamedTemporaryFile(mode="w", suffix=".js", delete=False) as fh:
            fh.write(_PART3_HARNESS_JS)
            path = fh.name
        try:
            proc = subprocess.run(
                [node_bin, path],
                capture_output=True, text=True, timeout=30,
            )
        finally:
            Path(path).unlink(missing_ok=True)
>       assert proc.returncode == 0, (
            f"PART 3 in-flight-poll harness exited {proc.returncode}\nSTDOUT:\n{proc.stdout}\nSTDERR:\n{proc.stderr}"
        )
E       AssertionError: PART 3 in-flight-poll harness exited 2
E         STDOUT:
E         After boot: curDay=2026-08-07 pollTimer=set
E         Pre-click: curDay=2026-08-07 calls=5
E         Click #tw-prev
E         After 100ms wait: curDay=2026-08-07 pollTimer=set _twNavPinned=true
E         All fetches:
E           0: date=2026-08-07
E           1: date=2026-08-07 (ABORTED)
E           2: date=2026-08-07
E           3: date=2026-08-07 (ABORTED)
E           4: date=2026-08-07
E           5: date=2026-08-07 (ABORTED)
E           6: date=2026-08-06
E           7: date=2026-08-06 (ABORTED)
E           8: date=2026-08-07
E           9: date=2026-08-07 (ABORTED)
E           10: date=2026-08-07
E           11: date=2026-08-07 (ABORTED)
E           12: date=2026-08-07
E           13: date=2026-08-07 (ABORTED)
E           14: date=2026-08-07
E           15: date=2026-08-07 (ABORTED)
E           16: date=2026-08-07
E           17: date=2026-08-07 (ABORTED)
E           18: date=2026-08-07
E           19: date=2026-08-07 (ABORTED)
E           20: date=2026-08-07
E           21: date=2026-08-07 (ABORTED)
E           22: date=2026-08-07
E           23: date=2026-08-07 (ABORTED)
E           24: date=2026-08-07
E           25: date=2026-08-07 (ABORTED)
E           26: date=2026-08-07
E         FAIL: 10 trailing non-aborted fetch(es) for today after click — page would snap back
E         
E         STDERR:
E         
E       assert 2 == 0
E        +  where 2 = CompletedProcess(args=['/opt/homebrew/bin/node', '/var/folders/yn/hd_3bcpj475dy17gy4l92tq00000gn/T/tmpgxqf7l2d.js'], returncode=2, stdout='After boot: curDay=2026-08-07 pollTimer=set\nPre-click: curDay=2026-08-07 calls=5\nClick #tw-prev\nAfter 100ms wait: curDay=2026-08-07 pollTimer=set _twNavPinned=true\nAll fetches:\n  0: date=2026-08-07\n  1: date=2026-08-07 (ABORTED)\n  2: date=2026-08-07\n  3: date=2026-08-07 (ABORTED)\n  4: date=2026-08-07\n  5: date=2026-08-07 (ABORTED)\n  6: date=2026-08-06\n  7: date=2026-08-06 (ABORTED)\n  8: date=2026-08-07\n  9: date=2026-08-07 (ABORTED)\n  10: date=2026-08-07\n  11: date=2026-08-07 (ABORTED)\n  12: date=2026-08-07\n  13: date=2026-08-07 (ABORTED)\n  14: date=2026-08-07\n  15: date=2026-08-07 (ABORTED)\n  16: date=2026-08-07\n  17: date=2026-08-07 (ABORTED)\n  18: date=2026-08-07\n  19: date=2026-08-07 (ABORTED)\n  20: date=2026-08-07\n  21: date=2026-08-07 (ABORTED)\n  22: date=2026-08-07\n  23: date=2026-08-07 (ABORTED)\n  24: date=2026-08-07\n  25: date=2026-08-07 (ABORTED)\n  26: date=2026-08-07\nFAIL: 10 trailing non-aborted fetch(es) for today after click — page would snap back\n', stderr='').returncode

tests/test_tide_wave_prev_button.py:761: AssertionError