fix(smoke): explicitly select known guest filesystems when mounting

tests/test_laptop_smoke.py

@@ -117,3 +117,27 @@ class LaptopSmokeTests(unittest.TestCase):
         self.assertNotIn('--offline', constants, 'emerge has no --offline option')
         self.assertIn('--ignore-default-opts', constants)
         self.assertIn('--nodeps', constants)
+
+    def test_guest_mount_explicitly_selects_known_filesystem(self):
+        namespace = {}
+        exec(self.mod.GUEST_COMMON, namespace)
+        calls = []
+        namespace['run'] = lambda *args: calls.append(args)
+        for device, filesystem, options in (('/dev/vda1', 'vfat', 'ro'),
+                                            ('/dev/vda2', 'ext4', 'ro'),
+                                            ('/dev/vda3', 'btrfs', 'ro,subvol=@root')):
+            with self.subTest(device=device):
+                with namespace['mounted'](device, filesystem, options) as directory:
+                    self.assertEqual(calls[-1], ('mount', '-t', filesystem, '-o', options, device, str(directory)))
+                self.assertEqual(calls[-1], ('umount', str(directory)))
+
+    def test_every_guest_mount_call_names_the_partition_filesystem(self):
+        import ast
+        expected = {'/dev/vda1': 'vfat', '/dev/vda2': 'ext4', '/dev/vda3': 'btrfs'}
+        sources = [self.mod.GUEST_COMMON, *self.mod.GUEST_BODIES.values()]
+        for source in sources:
+            for node in ast.walk(ast.parse(source)):
+                if isinstance(node, ast.Call) and isinstance(node.func, ast.Name) and node.func.id == 'mounted':
+                    with self.subTest(call=ast.unparse(node)):
+                        self.assertGreaterEqual(len(node.args), 2)
+                        self.assertEqual(ast.literal_eval(node.args[1]), expected[ast.literal_eval(node.args[0])])