Add new fixed_datetime and with_fixed_datetime functions to testing.py

Author: domdfcoding

domdf_python_tools/testing.py

@@ -54,6 +54,7 @@
 import os
 import random
 import sys
+from contextlib import contextmanager
 from functools import lru_cache
 from pathlib import Path
 from textwrap import dedent
@@ -62,6 +63,7 @@
 # 3rd party
 import pytest  # nodep
 from _pytest.mark import MarkDecorator  # nodep
+from pytest import MonkeyPatch  # nodep
 from pytest_regressions.file_regression import FileRegressionFixture  # nodep
 
 # this package
@@ -98,7 +100,9 @@
 		"tmp_pathplus",
 		"whitespace",
 		"whitespace_perms",
-		"whitespace_perms_list"
+		"whitespace_perms_list",
+		"fixed_datetime",
+		"with_fixed_datetime",
 		]
 
 MarkDecorator.__module__ = "_pytest.mark"
@@ -558,3 +562,89 @@ def check_file_output(
 		extension = "._py_"
 
 	return check_file_regression(data, file_regression, extension, newline=newline, **kwargs)
+
+
+@pytest.fixture()
+def fixed_datetime(monkeypatch):
+	"""
+	Pytest fixture to pretend the current datetime is 2:20 AM on 13th October 2020.
+
+	.. versionadded:: 2.2.0
+
+	.. seealso:: The :func:`with_fixed_datetime` contextmanager.
+
+	.. attention::
+
+		The monkeypatching only works when datetime is used and imported like:
+
+		.. code-block:: python
+
+			import datetime
+			print(datetime.datetime.now())
+
+		Using ``from datetime import datetime`` won't work.
+	"""
+
+	with with_fixed_datetime(datetime.datetime(2020, 10, 13, 2, 20)):
+		yield
+
+
+@contextmanager
+def with_fixed_datetime(fixed_datetime: datetime.datetime):
+	"""
+	Context manager to set a fixed datetime for the duration of the ``with`` block.
+
+	.. versionadded:: 2.2.0
+
+	:param fixed_datetime:
+
+	.. seealso:: The :fixture:`fixed_datetime` fixture.
+
+	.. attention::
+
+		The monkeypatching only works when datetime is used and imported like:
+
+		.. code-block:: python
+
+			import datetime
+			print(datetime.datetime.now())
+
+		Using ``from datetime import datetime`` won't work.
+	"""
+
+	class D(datetime.date):
+
+		@classmethod
+		def today(cls):
+			return datetime.date(
+					fixed_datetime.year,
+					fixed_datetime.month,
+					fixed_datetime.day,
+					)
+
+	class DT(datetime.datetime):
+
+		@classmethod
+		def today(cls):
+			return datetime.datetime(
+					fixed_datetime.year,
+					fixed_datetime.month,
+					fixed_datetime.day,
+					)
+
+		@classmethod
+		def now(cls, tz=None):
+			return datetime.datetime.fromtimestamp(fixed_datetime.timestamp())
+
+	D.__name__ = "date"
+	D.__qualname__ = "date"
+	DT.__qualname__ = "datetime"
+	DT.__name__ = "datetime"
+	D.__module__ = "datetime"
+	DT.__module__ = "datetime"
+
+	with MonkeyPatch.context() as monkeypatch:
+		monkeypatch.setattr(datetime, "date", D)
+		monkeypatch.setattr(datetime, "datetime", DT)
+
+		yield

repo_helper.yml

@@ -30,7 +30,7 @@ extras_require:
   dates:
    - pytz>=2019.1
   testing:
-   - pytest>=6.0.0
+   - pytest>=6.2.0
    - pytest-regressions>=2.0.2
 
 conda_extras:

tests/test_testing.py

@@ -1,4 +1,5 @@
 # stdlib
+import datetime
 import platform
 import random
 import re
@@ -20,7 +21,8 @@
 		only_macos,
 		only_pypy,
 		only_version,
-		only_windows
+		only_windows,
+		with_fixed_datetime
 		)
 from domdf_python_tools.utils import strtobool
 
@@ -221,3 +223,43 @@ def test_check_file_output(tmp_pathplus, file_regression: FileRegressionFixture)
 
 	(tmp_pathplus / "file.txt").write_text("Success!")
 	check_file_output(tmp_pathplus / "file.txt", file_regression)
+
+
+def test_fixed_datetime(fixed_datetime):
+	assert datetime.datetime.today() == datetime.datetime(2020, 10, 13)
+	assert datetime.datetime.now() == datetime.datetime(2020, 10, 13, 2, 20)
+
+	assert datetime.datetime.__name__ == "datetime"
+	assert datetime.datetime.__qualname__ == "datetime"
+	assert datetime.datetime.__module__ == "datetime"
+
+	assert datetime.date.today() == datetime.date(2020, 10, 13)
+
+	assert datetime.date.__name__ == "date"
+	assert datetime.date.__qualname__ == "date"
+	assert datetime.date.__module__ == "datetime"
+
+
+@pytest.mark.parametrize(
+		"fake_datetime, expected_date",
+		[
+				pytest.param(datetime.datetime(2020, 10, 13, 2, 20), datetime.datetime(2020, 10, 13), id='0'),
+				pytest.param(datetime.datetime(2020, 7, 4, 10, 00), datetime.datetime(2020, 7, 4), id='1'),
+				]
+		)
+def test_with_fixed_datetime(fake_datetime, expected_date):
+
+	with with_fixed_datetime(fake_datetime):
+		assert datetime.datetime.today() == expected_date
+		assert datetime.datetime.now() == fake_datetime
+
+		assert datetime.datetime.__name__ == "datetime"
+		assert datetime.datetime.__qualname__ == "datetime"
+		assert datetime.datetime.__module__ == "datetime"
+
+		assert datetime.date.today() == expected_date
+		assert isinstance(datetime.date.today(), datetime.date)
+
+		assert datetime.date.__name__ == "date"
+		assert datetime.date.__qualname__ == "date"
+		assert datetime.date.__module__ == "datetime"