Collector: machine number identifies the machine, not the PC; ntlars empty-value fix

tests/test_plugins/test_backups.py

@@ -710,3 +710,50 @@ def test_panel_label_is_rendered_in_the_site_zone(bk_app, bk_plugin):
         revision = _db.session.get(BackupRevision, result['backuprevisionid'])
         # 16:30 UTC on 2026-08-07 is 12:30 EDT.
         assert '12:30' in _label(revision)
+
+
+# =============================================================================
+# REGEDIT4 / part marker exports
+# =============================================================================
+
+REGEDIT4REG = (
+    'REGEDIT4\r\n\r\n'
+    r'[HKEY_LOCAL_MACHINE\SOFTWARE\GE Aircraft Engines\DNC\General]' '\r\n'
+    '"MachineNo"="WJPRT"\r\n'
+    '"Cnc"="MARKER"\r\n\r\n'
+    r'[HKEY_LOCAL_MACHINE\SOFTWARE\GE Aircraft Engines\DNC\Mark]' '\r\n'
+    '"Port Id"="COM4"\r\n'
+    '"Baud"="9600"\r\n'
+    '"KRelay1"=\r\n'
+)
+
+
+def test_regedit4_header_is_accepted():
+    """The part marker's per-machine file is REGEDIT4, not 'Windows Registry
+    Editor Version 5.00'."""
+    projection = ntlars.parse(REGEDIT4REG.encode('utf-8'))
+    assert registry.NtlarsKind.embeddedmachineno(projection) == 'WJPRT'
+
+
+def test_value_with_an_empty_right_hand_side_does_not_fail_the_file():
+    """A real export contains "KRelay1=" with nothing after the sign. Raising on
+    it would mean that machine could never be backed up at all."""
+    projection = ntlars.parse(REGEDIT4REG.encode('utf-8'))
+    mark = next(k for k in projection['keys'] if k['path'] == 'Mark')
+    assert mark['values']['KRelay1'] == {'type': 'REG_SZ', 'data': ''}
+
+
+def test_part_marker_serial_port_survives_the_roundtrip():
+    """The COM port the marker hangs off is the point of keeping this config."""
+    first = ntlars.parse(REGEDIT4REG.encode('utf-8'))
+    second = ntlars.parse(ntlars.render(first, dialect='wow6432node'))
+    mark = next(k for k in second['keys'] if k['path'] == 'Mark')
+    assert mark['values']['Port Id']['data'] == 'COM4'
+
+
+def test_a_marker_export_shows_the_mark_tab():
+    card = dncinfo.build(ntlars.parse(REGEDIT4REG.encode('utf-8')), assetid=0)
+    labels = [s['label'] for s in card['sections']]
+    assert any('MARK' in label for label in labels)
+    mark = next(s for s in card['sections'] if 'MARK' in s['label'])
+    assert any(f['label'] == 'Port Id' and f['value'] == 'COM4' for f in mark['fields'])