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- """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_timing" also interacts with this module for pytest's own tests.
- """
- from __future__ import annotations
- import dataclasses
- from datetime import datetime
- from datetime import timezone
- from time import perf_counter
- from time import sleep
- from time import time
- from typing import TYPE_CHECKING
- if TYPE_CHECKING:
- from pytest import MonkeyPatch
- @dataclasses.dataclass(frozen=True)
- class Instant:
- """
- Represents an instant in time, used to both get the timestamp value and to measure
- the duration of a time span.
- Inspired by Rust's `std::time::Instant`.
- """
- # Creation time of this instant, using time.time(), to measure actual time.
- # Note: using a `lambda` to correctly get the mocked time via `MockTiming`.
- time: float = dataclasses.field(default_factory=lambda: time(), init=False)
- # Performance counter tick of the instant, used to measure precise elapsed time.
- # Note: using a `lambda` to correctly get the mocked time via `MockTiming`.
- perf_count: float = dataclasses.field(
- default_factory=lambda: perf_counter(), init=False
- )
- def elapsed(self) -> Duration:
- """Measure the duration since `Instant` was created."""
- return Duration(start=self, stop=Instant())
- def as_utc(self) -> datetime:
- """Instant as UTC datetime."""
- return datetime.fromtimestamp(self.time, timezone.utc)
- @dataclasses.dataclass(frozen=True)
- class Duration:
- """A span of time as measured by `Instant.elapsed()`."""
- start: Instant
- stop: Instant
- @property
- def seconds(self) -> float:
- """Elapsed time of the duration in seconds, measured using a performance counter for precise timing."""
- return self.stop.perf_count - self.start.perf_count
- @dataclasses.dataclass
- class MockTiming:
- """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."""
- _current_time: float = datetime(2020, 5, 22, 14, 20, 50).timestamp()
- def sleep(self, seconds: float) -> None:
- self._current_time += seconds
- def time(self) -> float:
- return self._current_time
- def patch(self, monkeypatch: MonkeyPatch) -> None:
- # pylint: disable-next=import-self
- from _pytest import timing # noqa: PLW0406
- monkeypatch.setattr(timing, "sleep", self.sleep)
- monkeypatch.setattr(timing, "time", self.time)
- monkeypatch.setattr(timing, "perf_counter", self.time)
- __all__ = ["perf_counter", "sleep", "time"]
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