Add CLI arg to keep scratch files after test execution, equivalent to
setting QEMU_TEST_KEEP_SCRATCH env var.

Suggested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
---
 tests/functional/qemu_test/testcase.py | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/tests/functional/qemu_test/testcase.py b/tests/functional/qemu_test/testcase.py
index 3ecaaeffd4df2945fb4c44b4ddef6911527099b9..24f0b452964012532530a92018b2c4367b39fb77 100644
--- a/tests/functional/qemu_test/testcase.py
+++ b/tests/functional/qemu_test/testcase.py
@@ -43,6 +43,13 @@ def parse_args(test_name: str) -> argparse.Namespace:
         help="Also print test and console logs on stdout. This will make the"
         " TAP output invalid and is meant for debugging only.",
     )
+    parser.add_argument(
+        "--keep-scratch",
+        action="store_true",
+        help="Do not purge any scratch files created during the tests. "
+        "This is equivalent to setting QEMU_TEST_KEEP_SCRATCH=1 in the "
+        "environment.",
+    )
     return parser.parse_args()
 
 
@@ -214,6 +221,10 @@ def setUp(self):
         path = os.path.basename(sys.argv[0])[:-3]
         args = parse_args(path)
         self.stdout_handler = None
+        self.keep_scratch = (
+                "QEMU_TEST_KEEP_SCRATCH" in os.environ
+                or args.keep_scratch
+        )
         if args.debug:
             self.stdout_handler = logging.StreamHandler(sys.stdout)
             self.stdout_handler.setLevel(logging.DEBUG)
@@ -255,8 +266,10 @@ def setUp(self):
             self.skipTest('One or more assets is not available')
 
     def tearDown(self):
-        if "QEMU_TEST_KEEP_SCRATCH" not in os.environ:
+        if not self.keep_scratch:
             shutil.rmtree(self.workdir)
+        else:
+            self.log.info(f"Kept scratch files in {self.workdir}")
         if self.socketdir is not None:
             shutil.rmtree(self.socketdir.name)
             self.socketdir = None

-- 
2.47.2