Merge pull request #7242 from nicoddemus/fix-flaky-test

Introduce _pytest.timing as a way to control timing during internal tests

src/_pytest/junitxml.py

@@ -13,7 +13,6 @@ import os
 import platform
 import re
 import sys
-import time
 from datetime import datetime
 
 import py
@@ -21,6 +20,7 @@ import py
 import pytest
 from _pytest import deprecated
 from _pytest import nodes
+from _pytest import timing
 from _pytest.config import filename_arg
 from _pytest.store import StoreKey
 from _pytest.warnings import _issue_warning_captured
@@ -625,14 +625,14 @@ class LogXML:
         reporter._add_simple(Junit.error, "internal error", excrepr)
 
     def pytest_sessionstart(self):
-        self.suite_start_time = time.time()
+        self.suite_start_time = timing.time()
 
     def pytest_sessionfinish(self):
         dirname = os.path.dirname(os.path.abspath(self.logfile))
         if not os.path.isdir(dirname):
             os.makedirs(dirname)
         logfile = open(self.logfile, "w", encoding="utf-8")
-        suite_stop_time = time.time()
+        suite_stop_time = timing.time()
         suite_time_delta = suite_stop_time - self.suite_start_time
 
         numtests = (
@@ -660,7 +660,7 @@ class LogXML:
         logfile.close()
 
     def pytest_terminal_summary(self, terminalreporter):
-        terminalreporter.write_sep("-", "generated xml file: %s" % (self.logfile))
+        terminalreporter.write_sep("-", "generated xml file: {}".format(self.logfile))
 
     def add_global_property(self, name, value):
         __tracebackhide__ = True

src/_pytest/pytester.py

@@ -7,7 +7,6 @@ import platform
 import re
 import subprocess
 import sys
-import time
 import traceback
 from fnmatch import fnmatch
 from io import StringIO
@@ -24,6 +23,7 @@ from weakref import WeakKeyDictionary
 import py
 
 import pytest
+from _pytest import timing
 from _pytest._code import Source
 from _pytest.capture import _get_multicapture
 from _pytest.compat import TYPE_CHECKING
@@ -970,7 +970,7 @@ class Testdir:
 
         if syspathinsert:
             self.syspathinsert()
-        now = time.time()
+        now = timing.time()
         capture = _get_multicapture("sys")
         capture.start_capturing()
         try:
@@ -999,7 +999,7 @@ class Testdir:
             sys.stderr.write(err)
 
         res = RunResult(
-            reprec.ret, out.splitlines(), err.splitlines(), time.time() - now
+            reprec.ret, out.splitlines(), err.splitlines(), timing.time() - now
         )
         res.reprec = reprec  # type: ignore
         return res
@@ -1200,7 +1200,7 @@ class Testdir:
         f1 = open(str(p1), "w", encoding="utf8")
         f2 = open(str(p2), "w", encoding="utf8")
         try:
-            now = time.time()
+            now = timing.time()
             popen = self.popen(
                 cmdargs,
                 stdin=stdin,
@@ -1247,7 +1247,7 @@ class Testdir:
             ret = ExitCode(ret)
         except ValueError:
             pass
-        return RunResult(ret, out, err, time.time() - now)
+        return RunResult(ret, out, err, timing.time() - now)
 
     def _dump_lines(self, lines, fp):
         try:

src/_pytest/runner.py

@@ -2,8 +2,6 @@
 import bdb
 import os
 import sys
-from time import perf_counter  # Intentionally not `import time` to avoid being
-from time import time  # affected by tests which monkeypatch `time` (issue #185).
 from typing import Callable
 from typing import Dict
 from typing import List
@@ -15,6 +13,7 @@ import attr
 from .reports import CollectErrorRepr
 from .reports import CollectReport
 from .reports import TestReport
+from _pytest import timing
 from _pytest._code.code import ExceptionChainRepr
 from _pytest._code.code import ExceptionInfo
 from _pytest.compat import TYPE_CHECKING
@@ -254,8 +253,8 @@ class CallInfo:
         #: context of invocation: one of "setup", "call",
         #: "teardown", "memocollect"
         excinfo = None
-        start = time()
-        precise_start = perf_counter()
+        start = timing.time()
+        precise_start = timing.perf_counter()
         try:
             result = func()
         except BaseException:
@@ -264,9 +263,9 @@ class CallInfo:
                 raise
             result = None
         # use the perf counter
-        precise_stop = perf_counter()
+        precise_stop = timing.perf_counter()
         duration = precise_stop - precise_start
-        stop = time()
+        stop = timing.time()
         return cls(
             start=start,
             stop=stop,

src/_pytest/terminal.py

@@ -7,7 +7,6 @@ import datetime
 import inspect
 import platform
 import sys
-import time
 import warnings
 from functools import partial
 from typing import Any
@@ -26,6 +25,7 @@ from more_itertools import collapse
 
 import pytest
 from _pytest import nodes
+from _pytest import timing
 from _pytest._io import TerminalWriter
 from _pytest._io.wcwidth import wcswidth
 from _pytest.compat import order_preserving_dict
@@ -552,7 +552,7 @@ class TerminalReporter:
         if self.isatty:
             if self.config.option.verbose >= 0:
                 self.write("collecting ... ", flush=True, bold=True)
-                self._collect_report_last_write = time.time()
+                self._collect_report_last_write = timing.time()
         elif self.config.option.verbose >= 1:
             self.write("collecting ... ", flush=True, bold=True)
 
@@ -572,7 +572,7 @@ class TerminalReporter:
 
         if not final:
             # Only write "collecting" report every 0.5s.
-            t = time.time()
+            t = timing.time()
             if (
                 self._collect_report_last_write is not None
                 and self._collect_report_last_write > t - REPORT_COLLECTING_RESOLUTION
@@ -609,7 +609,7 @@ class TerminalReporter:
     @pytest.hookimpl(trylast=True)
     def pytest_sessionstart(self, session: Session) -> None:
         self._session = session
-        self._sessionstarttime = time.time()
+        self._sessionstarttime = timing.time()
         if not self.showheader:
             return
         self.write_sep("=", "test session starts", bold=True)
@@ -964,7 +964,7 @@ class TerminalReporter:
         if self.verbosity < -1:
             return
 
-        session_duration = time.time() - self._sessionstarttime
+        session_duration = timing.time() - self._sessionstarttime
         (parts, main_color) = self.build_summary_stats_line()
         line_parts = []
 

src/_pytest/timing.py

@@ -0,0 +1,13 @@
+"""
+Indirection for time functions.
+
+We intentionally grab some "time" functions internally to avoid tests mocking "time" to affect
+pytest runtime information (issue #185).
+
+Fixture "mock_timinig" also interacts with this module for pytest's own tests.
+"""
+from time import perf_counter
+from time import sleep
+from time import time
+
+__all__ = ["perf_counter", "sleep", "time"]

testing/acceptance_test.py

@@ -6,11 +6,9 @@ import types
 import attr
 import py
 
-import _pytest.runner
 import pytest
 from _pytest.compat import importlib_metadata
 from _pytest.config import ExitCode
-from _pytest.monkeypatch import MonkeyPatch
 from _pytest.pytester import Testdir
 
 
@@ -896,37 +894,21 @@ class TestInvocationVariants:
         assert request.config.pluginmanager.hasplugin("python")
 
 
-def fake_time(monkeypatch: MonkeyPatch) -> None:
-    """Monkeypatch time functions to make TestDurations not rely on actual time."""
-    import time
-
-    current_time = 1586202699.9859412
-
-    def sleep(seconds: float) -> None:
-        nonlocal current_time
-        current_time += seconds
-
-    monkeypatch.setattr(time, "sleep", sleep)
-    monkeypatch.setattr(_pytest.runner, "time", lambda: current_time)
-    monkeypatch.setattr(_pytest.runner, "perf_counter", lambda: current_time)
-
-
 class TestDurations:
     source = """
-        import time
+        from _pytest import timing
         def test_something():
             pass
         def test_2():
-            time.sleep(0.010)
+            timing.sleep(0.010)
         def test_1():
-            time.sleep(0.002)
+            timing.sleep(0.002)
         def test_3():
-            time.sleep(0.020)
+            timing.sleep(0.020)
     """
 
-    def test_calls(self, testdir):
+    def test_calls(self, testdir, mock_timing):
         testdir.makepyfile(self.source)
-        fake_time(testdir.monkeypatch)
         result = testdir.runpytest_inprocess("--durations=10")
         assert result.ret == 0
 
@@ -938,18 +920,17 @@ class TestDurations:
             ["(8 durations < 0.005s hidden.  Use -vv to show these durations.)"]
         )
 
-    def test_calls_show_2(self, testdir):
+    def test_calls_show_2(self, testdir, mock_timing):
+
         testdir.makepyfile(self.source)
-        fake_time(testdir.monkeypatch)
         result = testdir.runpytest_inprocess("--durations=2")
         assert result.ret == 0
 
         lines = result.stdout.get_lines_after("*slowest*durations*")
         assert "4 passed" in lines[2]
 
-    def test_calls_showall(self, testdir):
+    def test_calls_showall(self, testdir, mock_timing):
         testdir.makepyfile(self.source)
-        fake_time(testdir.monkeypatch)
         result = testdir.runpytest_inprocess("--durations=0")
         assert result.ret == 0
 
@@ -962,9 +943,8 @@ class TestDurations:
                 else:
                     raise AssertionError("not found {} {}".format(x, y))
 
-    def test_calls_showall_verbose(self, testdir):
+    def test_calls_showall_verbose(self, testdir, mock_timing):
         testdir.makepyfile(self.source)
-        fake_time(testdir.monkeypatch)
         result = testdir.runpytest_inprocess("--durations=0", "-vv")
         assert result.ret == 0
 
@@ -976,17 +956,15 @@ class TestDurations:
                 else:
                     raise AssertionError("not found {} {}".format(x, y))
 
-    def test_with_deselected(self, testdir):
+    def test_with_deselected(self, testdir, mock_timing):
         testdir.makepyfile(self.source)
-        fake_time(testdir.monkeypatch)
         result = testdir.runpytest_inprocess("--durations=2", "-k test_3")
         assert result.ret == 0
 
         result.stdout.fnmatch_lines(["*durations*", "*call*test_3*"])
 
-    def test_with_failing_collection(self, testdir):
+    def test_with_failing_collection(self, testdir, mock_timing):
         testdir.makepyfile(self.source)
-        fake_time(testdir.monkeypatch)
         testdir.makepyfile(test_collecterror="""xyz""")
         result = testdir.runpytest_inprocess("--durations=2", "-k test_1")
         assert result.ret == 2
@@ -996,9 +974,8 @@ class TestDurations:
         # output
         result.stdout.no_fnmatch_line("*duration*")
 
-    def test_with_not(self, testdir):
+    def test_with_not(self, testdir, mock_timing):
         testdir.makepyfile(self.source)
-        fake_time(testdir.monkeypatch)
         result = testdir.runpytest_inprocess("-k not 1")
         assert result.ret == 0
 
@@ -1006,27 +983,26 @@ class TestDurations:
 class TestDurationsWithFixture:
     source = """
         import pytest
-        import time
+        from _pytest import timing
 
         @pytest.fixture
         def setup_fixt():
-            time.sleep(0.02)
+            timing.sleep(2)
 
         def test_1(setup_fixt):
-            time.sleep(0.02)
+            timing.sleep(5)
     """
 
-    def test_setup_function(self, testdir):
+    def test_setup_function(self, testdir, mock_timing):
         testdir.makepyfile(self.source)
-        fake_time(testdir.monkeypatch)
         result = testdir.runpytest_inprocess("--durations=10")
         assert result.ret == 0
 
         result.stdout.fnmatch_lines_random(
             """
             *durations*
-            * setup *test_1*
-            * call *test_1*
+            5.00s call *test_1*
+            2.00s setup *test_1*
         """
         )
 

testing/conftest.py

@@ -197,3 +197,41 @@ def color_mapping():
                 )
 
     return ColorMapping
+
+
+@pytest.fixture
+def mock_timing(monkeypatch):
+    """Mocks _pytest.timing with a known object that can be used to control timing in tests
+    deterministically.
+
+    pytest itself should always use functions from `_pytest.timing` instead of `time` directly.
+
+    This then allows us more control over time during testing, if testing code also
+    uses `_pytest.timing` functions.
+
+    Time is static, and only advances through `sleep` calls, thus tests might sleep over large
+    numbers and obtain accurate time() calls at the end, making tests reliable and instant.
+    """
+    import attr
+
+    @attr.s
+    class MockTiming:
+
+        _current_time = attr.ib(default=1590150050.0)
+
+        def sleep(self, seconds):
+            self._current_time += seconds
+
+        def time(self):
+            return self._current_time
+
+        def patch(self):
+            from _pytest import timing
+
+            monkeypatch.setattr(timing, "sleep", self.sleep)
+            monkeypatch.setattr(timing, "time", self.time)
+            monkeypatch.setattr(timing, "perf_counter", self.time)
+
+    result = MockTiming()
+    result.patch()
+    return result

testing/test_junitxml.py

@@ -201,23 +201,23 @@ class TestPython:
         timestamp = datetime.strptime(node["timestamp"], "%Y-%m-%dT%H:%M:%S.%f")
         assert start_time <= timestamp < datetime.now()
 
-    def test_timing_function(self, testdir, run_and_parse):
+    def test_timing_function(self, testdir, run_and_parse, mock_timing):
         testdir.makepyfile(
             """
-            import time, pytest
+            from _pytest import timing
             def setup_module():
-                time.sleep(0.01)
+                timing.sleep(1)
             def teardown_module():
-                time.sleep(0.01)
+                timing.sleep(2)
             def test_sleep():
-                time.sleep(0.01)
+                timing.sleep(4)
         """
         )
         result, dom = run_and_parse()
         node = dom.find_first_by_tag("testsuite")
         tnode = node.find_first_by_tag("testcase")
         val = tnode["time"]
-        assert round(float(val), 2) >= 0.03
+        assert float(val) == 7.0
 
     @pytest.mark.parametrize("duration_report", ["call", "total"])
     def test_junit_duration_report(