Improve the management of workdir cleanup for debugging purposes (#221)

- In case of test failure, we would like that the workdir of qemu
  is not cleaned up so that we can do some debugging.
- Improve the management of environment variable TDXTEST_DEBUG
  that forbids the clean up of these workdirs at any case

tests/lib/Qemu.py

@@ -430,20 +430,21 @@ class QemuMachineService:
     QEMU_MACHINE_QMP = enum.auto()
 
 class QemuMachine:
+    debug_enabled = False
+
     def __init__(self,
                  name='default',
                  machine=QemuEfiMachine.OVMF_Q35_TDX,
                  memory='2G',
                  service_blacklist=[]):
         self.name = name
-        self.debug = os.environ.get('TDXTEST_DEBUG', False)
         self.image_dir = '/var/tmp/tdxtest/'
         self.guest_initial_img = os.environ.get('TDXTEST_GUEST_IMG', f'{self.image_dir}/tdx-guest.qcow2')
         self._setup_workdir()
         self._create_image()
 
         # TODO : WA for log, to be removed
-        print(f'\n\nQemuMachine created (debug={self.debug}).')
+        print(f'\n\nQemuMachine created.')
 
         self.qcmd = QemuCommand(
             self.workdir_name,
@@ -463,6 +464,14 @@ def __init__(self,
         self.out = None
         self.err = None
 
+    @staticmethod
+    def is_debug_enabled():
+        return QemuMachine.debug_enabled
+
+    @staticmethod
+    def set_debug(debug : bool):
+        QemuMachine.debug_enabled = debug
+
     def _create_image(self):
         # create an overlay image backed by the original image
         # See https://wiki.qemu.org/Documentation/CreateSnapshot
@@ -475,9 +484,10 @@ def _setup_workdir(self):
         run_path = pathlib.Path('/run/user/%d/' % (os.getuid()))
         if run_path.exists():
             tempfile.tempdir = str(run_path)
+        # delete=False : we want to manage cleanup ourself for debugging purposes
         # delete parameter is only available from 3.12
         if (sys.version_info[0]==3) and (sys.version_info[1]>11):
-            self.workdir = tempfile.TemporaryDirectory(prefix=f'tdxtest-{self.name}-', delete=not self.debug)
+            self.workdir = tempfile.TemporaryDirectory(prefix=f'tdxtest-{self.name}-', delete=False)
         else:
             self.workdir = tempfile.TemporaryDirectory(prefix=f'tdxtest-{self.name}-')
         self.workdir_name = self.workdir.name
@@ -554,5 +564,6 @@ def __del__(self):
         Make sure we stop the qemu process and clean up the working dir
         """
         self.stop()
-        if not self.debug:
+        needs_cleanup = (not QemuMachine.is_debug_enabled())
+        if needs_cleanup:
             self.workdir.cleanup()

tests/tests/conftest.py

@@ -0,0 +1,28 @@
+import os
+import pytest
+
+import Qemu
+
+@pytest.fixture(autouse=True)
+def run_before_and_after_tests(tmpdir):
+    """
+    Fixture to execute before and after a test is run
+    Even in case of test failure
+    """
+    # Setup: fill with any logic you want
+    # enable the debug flag if TDXTEST_DEBUG is set
+    debug = os.environ.get('TDXTEST_DEBUG', False)
+    if debug:
+        Qemu.QemuMachine.set_debug(debug)
+
+    yield # this is where the testing happens
+
+    # Teardown : fill with any logic you want
+
+def pytest_exception_interact(node, call, report):
+    """
+    Called at test failure
+    """
+    if report.failed:
+        # enable debug flag to avoid cleanup to happen
+        Qemu.QemuMachine.set_debug(True)