fix(test): select persistent UEFI test media without changing boot order

tests/test_iso_smoke.py

@@ -63,6 +63,30 @@ class SmokeTests(unittest.TestCase):
         self.assertNotIn('media=cdrom', ' '.join(argv))
         self.assertNotIn('-cdrom', argv)
 
+    def test_persistent_optical_drive_keeps_topology_with_no_installed_medium(self):
+        disk = self.root / 'disk.qcow2'
+        self.mod.reserve_disk(disk)
+        iso = self.root / 'trusted.iso'
+        iso.write_bytes(b'ISO')
+        optical = []
+        for medium in (iso, None):
+            argv = self.mod.qemu_argv('qemu', self.root, disk, self.code,
+                self.variables, medium, 2048, keep_cdrom_drive=True)
+            drives = [argv[i + 1] for i, value in enumerate(argv[:-1]) if value == '-drive']
+            cdrom = [dict(field.split('=', 1) for field in drive.split(','))
+                     for drive in drives if 'media=cdrom' in drive]
+            self.assertEqual(len(cdrom), 1)
+            self.assertEqual(cdrom[0]['if'], 'ide')
+            self.assertEqual(cdrom[0]['index'], '0')
+            self.assertEqual(cdrom[0]['id'], 'acceptance-cdrom')
+            self.assertEqual(cdrom[0]['readonly'], 'on')
+            optical.append(cdrom[0])
+        self.assertEqual(optical[0].pop('file'), str(iso))
+        self.assertEqual(optical[0].pop('format'), 'raw')
+        self.assertNotIn('file', optical[1], 'Installed boot must have no ISO medium')
+        self.assertNotIn('format', optical[1], 'An empty drive must not request a raw block backend')
+        self.assertEqual(optical[0], optical[1])
+
     def test_hardlinked_disk_is_refused(self):
         disk = self.root / 'disk.qcow2'
         self.mod.reserve_disk(disk)