pytest can report negative duration due to usage of time.time() #13384
Description
cutting most of the details here -- I'm using pytest 8.3.5 and just got this surprising result:
$ pytest tests/check_merge_conflict_test.py ============================= test session starts ============================== platform linux -- Python 3.12.3, pytest-8.3.5, pluggy-1.5.0 rootdir: /home/asottile/workspace/pre-commit-hooks collected 12 items tests/check_merge_conflict_test.py ............ [100%] ============================= 12 passed in -0.94s ==============================my tests are pretty fast but definitely not time-travelling fast.
it seems the root cause is usage of time.time() which is subject to smear seconds, etc. and should instead be using time.monotonic() or perf_counter()
seems there's a bunch of places we should adjust:
$ git grep '\btime\(\)' -- '*.py' src/_pytest/junitxml.py: self.suite_start_time = timing.time() src/_pytest/junitxml.py: suite_stop_time = timing.time() src/_pytest/pytester.py: now = timing.time() src/_pytest/pytester.py: reprec.ret, out.splitlines(), err.splitlines(), timing.time() - now src/_pytest/pytester.py: now = timing.time() src/_pytest/pytester.py: return RunResult(ret, out, err, timing.time() - now) src/_pytest/runner.py: start = timing.time() src/_pytest/runner.py: stop = timing.time() src/_pytest/terminal.py: self._collect_report_last_write = timing.time() src/_pytest/terminal.py: t = timing.time() src/_pytest/terminal.py: self._sessionstarttime = timing.time() src/_pytest/terminal.py: session_duration = timing.time() - self._sessionstarttime src/_pytest/timing.py: numbers and obtain accurate time() calls at the end, making tests reliable and instant.""" testing/_py/test_local.py: mtime = int(time.time()) - 100 testing/_py/test_local.py: now = time.time() testing/_py/test_local.py: duration = time.time() - now testing/conftest.py: numbers and obtain accurate time() calls at the end, making tests reliable and instant. testing/test_pytester.py: start = time.time() testing/test_pytester.py: end = time.time()