subtests: fix negative duration when the clock is mocked

changelog/15277.bugfix.rst

@@ -0,0 +1 @@
+Fixed negative durations being reported for subtests when the clock is mocked or frozen.

src/_pytest/subtests.py

@@ -11,13 +11,13 @@
 from contextlib import ExitStack
 from contextlib import nullcontext
 import dataclasses
-import time
 from types import TracebackType
 from typing import Any
 from typing import TYPE_CHECKING
 
 import pluggy
 
+from _pytest import timing
 from _pytest._code import ExceptionInfo
 from _pytest._io.saferepr import saferepr
 from _pytest.capture import CaptureFixture
@@ -216,8 +216,7 @@ class _SubTestContextManager:
     def __enter__(self) -> None:
         __tracebackhide__ = True
 
-        self._start = time.time()
-        self._precise_start = time.perf_counter()
+        self._timing = timing.Instant()
         self._exc_info = None
 
         self._exit_stack = ExitStack()
@@ -242,16 +241,14 @@ def __exit__(
 
         self._exit_stack.close()
 
-        precise_stop = time.perf_counter()
-        duration = precise_stop - self._precise_start
-        stop = time.time()
+        duration = self._timing.elapsed()
 
         call_info = CallInfo[None](
             None,
             exc_info,
-            start=self._start,
-            stop=stop,
-            duration=duration,
+            start=duration.start.time,
+            stop=duration.stop.time,
+            duration=duration.seconds,
             when="call",
             _ispytest=True,
         )

testing/test_subtests.py

@@ -1096,3 +1096,24 @@ def test(self):
     pytester.syspathinsert()
     result = pytester.runpytest("-n1", "-pxdist.plugin")
     result.assert_outcomes(passed=2)
+
+
+def test_subtest_with_mocked_clock(pytester: pytest.Pytester) -> None:
+    pytester.makepyfile(
+        """
+        import time
+
+        def test_with_subtest(subtests, monkeypatch):
+            real_sleep = time.sleep
+            monkeypatch.setattr(time, "perf_counter", lambda: 0.0)
+            monkeypatch.setattr(time, "time", lambda: 0.0)
+
+            with subtests.test("frozen clock"):
+                real_sleep(0.01)
+        """
+    )
+    result = pytester.runpytest("--junitxml=report.xml")
+    result.assert_outcomes(passed=1)
+
+    xml = pytester.path.joinpath("report.xml").read_text()
+    assert 'time="-' not in xml