From f74cc3a8d73c29090ee1f97f6b16da7539356241 Mon Sep 17 00:00:00 2001
From: Spencer Clark <spencerkclark@gmail.com>
Date: Sat, 28 Dec 2024 16:42:08 -0500
Subject: [PATCH] Add hypothesis strategy for cftime objects

---
 properties/test_encode_decode.py | 13 ++++++++----
 xarray/testing/strategies.py     | 34 ++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/properties/test_encode_decode.py b/properties/test_encode_decode.py
index 211c33ff6b5..374c6b33b93 100644
--- a/properties/test_encode_decode.py
+++ b/properties/test_encode_decode.py
@@ -5,6 +5,8 @@
 
 """
 
+import warnings
+
 import pytest
 
 pytest.importorskip("hypothesis")
@@ -17,7 +19,8 @@
 
 import xarray as xr
 from xarray.coding.times import _parse_iso8601_without_reso
-from xarray.testing.strategies import variables
+from xarray.testing.strategies import CFTimeStrategyISO8601, variables
+from xarray.tests import requires_cftime
 
 
 @pytest.mark.slow
@@ -47,8 +50,10 @@ def test_CFScaleOffset_coder_roundtrip(original) -> None:
     xr.testing.assert_identical(original, roundtripped)
 
 
-# TODO: add cftime.datetime
-@given(dt=st.datetimes())
+@requires_cftime
+@given(dt=st.datetimes() | CFTimeStrategyISO8601())
 def test_iso8601_decode(dt):
     iso = dt.isoformat()
-    assert dt == _parse_iso8601_without_reso(type(dt), iso)
+    with warnings.catch_warnings():
+        warnings.filterwarnings("ignore", message=".*date/calendar/year zero.*")
+        assert dt == _parse_iso8601_without_reso(type(dt), iso)
diff --git a/xarray/testing/strategies.py b/xarray/testing/strategies.py
index cfa226d991c..340988f8036 100644
--- a/xarray/testing/strategies.py
+++ b/xarray/testing/strategies.py
@@ -1,3 +1,5 @@
+import datetime
+import warnings
 from collections.abc import Hashable, Iterable, Mapping, Sequence
 from typing import TYPE_CHECKING, Any, Protocol, overload
 
@@ -8,6 +10,7 @@
 import xarray as xr
 from xarray.core.types import T_DuckArray
 from xarray.core.utils import attempt_import
+from xarray.tests.test_coding_times import _all_cftime_date_types
 
 if TYPE_CHECKING:
     from xarray.core.types import _DTypeLikeNested, _ShapeLike
@@ -473,3 +476,34 @@ def unique_subset_of(
     return (
         {k: objs[k] for k in subset_keys} if isinstance(objs, Mapping) else subset_keys
     )
+
+
+class CFTimeStategy(st.SearchStrategy):
+    def __init__(self, min_value, max_value):
+        self.min_value = min_value
+        self.max_value = max_value
+
+    def do_draw(self, data):
+        unit_microsecond = datetime.timedelta(microseconds=1)
+        timespan_microseconds = (self.max_value - self.min_value) // unit_microsecond
+        result = data.draw_integer(0, timespan_microseconds)
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", message=".*date/calendar/year zero.*")
+            return self.min_value + datetime.timedelta(microseconds=result)
+
+
+class CFTimeStrategyISO8601(st.SearchStrategy):
+    def __init__(self):
+        self.date_types = _all_cftime_date_types()
+        self.calendars = list(self.date_types)
+
+    def do_draw(self, data):
+        calendar = data.draw(st.sampled_from(self.calendars))
+        date_type = self.date_types[calendar]
+        with warnings.catch_warnings():
+            warnings.filterwarnings("ignore", message=".*date/calendar/year zero.*")
+            daysinmonth = date_type(99999, 12, 1).daysinmonth
+            min_value = date_type(-99999, 1, 1)
+            max_value = date_type(99999, 12, daysinmonth, 23, 59, 59, 999999)
+            strategy = CFTimeStategy(min_value, max_value)
+            return strategy.do_draw(data)