Beispiel

Freeze the clock in a Python test with freezegun so datetime, time.time and time.monotonic agree, and know what freeze_time cannot reach

sha256:e0a5abccbe96dde0a46b9b65aae94c3d5ffaa94f5eac58c72b82bec2141a0bfa

Fall

Ziel

Freeze the clock in a Python test with freezegun so datetime, time.time and time.monotonic agree, and know what freeze_time cannot reach HOW

Pakete

freezegun 1.5.5 python-dateutil 2.9.0.post0 six 1.17.0

Umgebung

python 3.12

Erstellt

2026-08-14T13:20:26Z

Contract

• assert freeze_time as a context manager pins datetime.now(), datetime.utcnow(), time.time(), time.time_ns() and date.today() to one instant that does not tick between reads
• assert the frozen readings agree with each other, so datetime.now().timestamp() is exactly time.time()
• assert a module that did `from datetime import datetime` before the freeze is frozen too, because freeze_time rebinds the name that module already holds
• assert freeze_time rewrites the test file's own globals as well, so a bare handle kept for comparison becomes the fake class and compares equal to it
• assert a bound classmethod captured at import (now = datetime.now) escapes the sweep and keeps returning real time inside the freeze
• assert a module-level constant computed at import (DEFAULT_START = datetime.now()) keeps its real value and its real class, and still passes isinstance against the frozen datetime
• assert a duration measured against that stale constant comes out negative by more than twenty-five years with nothing raised
• assert a datetime subclass defined at import ignores the freeze in now() but follows it in today(), because CPython builds today() on time.time and now() on the C system clock
• assert tick() advances one second and returns the new time, and tick(timedelta) and tick(float) advance further, with time.time() moving alongside
• assert move_to() sets an absolute time, returns None, and carries the module's readings and the subclass's today() with it
• assert time.monotonic and time.perf_counter are frozen to the same wall clock as time.time, so a duration spanning the boundary of the freeze measures about thirty years
• assert moving the frozen clock backwards makes time.monotonic() go backwards
• assert a module first imported inside the freeze keeps the frozen constant, as a FakeDatetime instance, after the block ends
• assert leaving the block restores datetime, the rewritten module globals and the real monotonic clock
• assert tz_offset is added to now() but never to utcnow(), so those two are what differ by the offset
• assert an aware now(timezone.utc) carries the same reading as the naive now() rather than a UTC-correct one, so its timestamp() disagrees with time.time() by exactly tz_offset
• assert the naive now().timestamp() equals time.time(), and date.today() takes the offset so a large enough offset changes the date
• assert tz_offset accepts a timedelta, so an offset that is not a whole number of hours works
• assert datetime.utcnow() raises a DeprecationWarning on python 3.12 in real time and none at all under a freeze

Dateien

• csx.json
• requirements.txt
• src/__init__.py
• src/clock.py
• src/late_import.py
• test/contract.py

Ursprungs-Seeder

anonymous

Verifizierungsbelege

• python 3.12 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · python@1 · 2026-08-14 · ed25519:a2ec939a4c60e243
• · CONTAINER_RUN · compile:SKIPPED · contract:FAIL · load:SKIPPED · resolve:PASS · python@1 · 2026-08-14 · ed25519:7da3f610facce8bf