Feature or enhancement
Some tests need to run in a fresh interpreter, isolated from the rest of the test run: they mutate process-global or interpreter state that would leak into (or be polluted by) other tests, depend on a clean interpreter startup, or may crash the interpreter outright. Today this has to be done ad hoc per test (spawning a child via script_helper, hand-rolling the result reporting), which is verbose and inconsistent.
I propose a decorator that runs a test in a dedicated subprocess and reports the result transparently, so the test reads like any other:
class MyTest(unittest.TestCase):
@isolated()
def test_global_state(self):
...It would start in test.support and could later move to unittest.
Proposed behaviour
@isolated() decorates a test method (only that method runs in a subprocess) or a whole TestCase subclass (the whole class runs in a single subprocess, so setUpClass()/setUpModule() run once there).- Failures, errors and skips — including those of individual
subTest()s — are reported for the corresponding test, and show the original subprocess traceback.
- A
setUpClass()/setUpModule() failure or skip in the subprocess is reported for the whole class.
- The subprocess inherits the parent's regrtest configuration (enabled resources
-u, memory limit -M, verbosity -v, failfast), so requires_resource(), requires(), bigmemtest() and similar behave the same in both processes.
- A
running_isolated flag is true while running in the subprocess, so setUp()/tearDown() and the class- and module-level fixtures can choose what to run there.
Linked PRs
Linked PRs
Feature or enhancement
Some tests need to run in a fresh interpreter, isolated from the rest of the test run: they mutate process-global or interpreter state that would leak into (or be polluted by) other tests, depend on a clean interpreter startup, or may crash the interpreter outright. Today this has to be done ad hoc per test (spawning a child via
script_helper, hand-rolling the result reporting), which is verbose and inconsistent.I propose a decorator that runs a test in a dedicated subprocess and reports the result transparently, so the test reads like any other:
It would start in
test.supportand could later move tounittest.Proposed behaviour
@isolated()decorates a test method (only that method runs in a subprocess) or a wholeTestCasesubclass (the whole class runs in a single subprocess, sosetUpClass()/setUpModule()run once there).subTest()s — are reported for the corresponding test, and show the original subprocess traceback.setUpClass()/setUpModule()failure or skip in the subprocess is reported for the whole class.-u, memory limit-M, verbosity-v, failfast), sorequires_resource(),requires(),bigmemtest()and similar behave the same in both processes.running_isolatedflag is true while running in the subprocess, sosetUp()/tearDown()and the class- and module-level fixtures can choose what to run there.Linked PRs
Linked PRs