general: make time.tz.via_location user config lazy, move tests to my.tests package

also gets rid of the problematic reset_modules thingie

my/tests/tz.py

@@ -0,0 +1,107 @@
+import sys
+from datetime import datetime, timedelta
+
+import pytest
+import pytz
+
+import my.time.tz.main as tz_main
+import my.time.tz.via_location as tz_via_location
+from my.core import notnone
+from my.core.compat import fromisoformat
+
+from .shared_tz_config import config  # autoused fixture
+
+
+def getzone(dt: datetime) -> str:
+    tz = notnone(dt.tzinfo)
+    return getattr(tz, 'zone')
+
+
+@pytest.mark.parametrize('fast', [False, True])
+def test_iter_tzs(fast: bool, config) -> None:
+    # TODO hmm.. maybe need to make sure we start with empty config?
+    config.time.tz.via_location.fast = fast
+
+    ll = list(tz_via_location._iter_tzs())
+    zones = [x.zone for x in ll]
+
+    if fast:
+        assert zones == [
+            'Europe/Rome',
+            'Europe/Rome',
+            'Europe/Vienna',
+            'Europe/Vienna',
+            'Europe/Vienna',
+        ]
+    else:
+        assert zones == [
+            'Europe/Rome',
+            'Europe/Rome',
+            'Europe/Ljubljana',
+            'Europe/Ljubljana',
+            'Europe/Ljubljana',
+        ]
+
+
+def test_past() -> None:
+    """
+    Should fallback to the 'home' location provider
+    """
+    dt = fromisoformat('2000-01-01 12:34:45')
+    dt = tz_main.localize(dt)
+    assert getzone(dt) == 'America/New_York'
+
+
+def test_future() -> None:
+    """
+    For locations in the future should rely on 'home' location
+    """
+    fut = datetime.now() + timedelta(days=100)
+    fut = tz_main.localize(fut)
+    assert getzone(fut) == 'Europe/Moscow'
+
+
+def test_get_tz(config) -> None:
+    # todo hmm, the way it's implemented at the moment, never returns None?
+    get_tz = tz_via_location.get_tz
+
+    # not present in the test data
+    tz = get_tz(fromisoformat('2020-01-01 10:00:00'))
+    assert notnone(tz).zone == 'Europe/Sofia'
+
+    tz = get_tz(fromisoformat('2017-08-01 11:00:00'))
+    assert notnone(tz).zone == 'Europe/Vienna'
+
+    tz = get_tz(fromisoformat('2017-07-30 10:00:00'))
+    assert notnone(tz).zone == 'Europe/Rome'
+
+    tz = get_tz(fromisoformat('2020-10-01 14:15:16'))
+    assert tz is not None
+
+    on_windows = sys.platform == 'win32'
+    if not on_windows:
+        tz = get_tz(datetime.min)
+        assert tz is not None
+    else:
+        # seems this fails because windows doesn't support same date ranges
+        # https://stackoverflow.com/a/41400321/
+        with pytest.raises(OSError):
+            get_tz(datetime.min)
+
+
+def test_policies() -> None:
+    naive = fromisoformat('2017-07-30 10:00:00')
+    assert naive.tzinfo is None  # just in case
+
+    # actual timezone at the time
+    assert getzone(tz_main.localize(naive)) == 'Europe/Rome'
+
+    z = pytz.timezone('America/New_York')
+    aware = z.localize(naive)
+
+    assert getzone(tz_main.localize(aware)) == 'America/New_York'
+
+    assert getzone(tz_main.localize(aware, policy='convert')) == 'Europe/Rome'
+
+    with pytest.raises(RuntimeError):
+        assert tz_main.localize(aware, policy='throw')