tests/functional: Add a decorator for skipping long running tests

Some tests have a very long runtime and might run into timeout issues
e.g. when QEMU has been compiled with --enable-debug. Add a decorator
for marking them more easily. Rename the corresponding environment
variable to be more in sync with the other QEMU_TEST_ALLOW_* switches
that we already have, and add a paragraph about it in the documentation.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20250128152839.184599-2-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/docs/devel/testing/functional.rst b/docs/devel/testing/functional.rst
index ae238ed3fc..ecc738922b 100644
--- a/docs/devel/testing/functional.rst
+++ b/docs/devel/testing/functional.rst
@@ -351,5 +351,13 @@ the code snippet below:
 Tests should not live in this state forever and should either be fixed
 or eventually removed.
 
+QEMU_TEST_ALLOW_SLOW
+^^^^^^^^^^^^^^^^^^^^
+Tests that have a very long runtime and might run into timeout issues
+e.g. if the QEMU binary has been compiled with debugging options enabled.
+To avoid these timeout issues by default and to save some precious CPU
+cycles during normal testing, such tests are disabled by default unless
+the QEMU_TEST_ALLOW_SLOW environment variable has been set.
+
 
 .. _unittest: https://docs.python.org/3/library/unittest.html