MDP-448 to_dt should respect default_tz for ms since epoch datetimes

        Add unit tests

Author: jamesblackburn

Diff for: arctic/date/_util.py

@@ -89,7 +89,7 @@ def to_dt(date, default_tz=None):
     date : `int` or `datetime.datetime`
         The datetime to convert
 
-    default_tz : tz_info
+    default_tz : tzinfo
         The TimeZone to use if none is found.  If not supplied, and the
         datetime doesn't have a timezone, then we raise ValueError
 
@@ -98,7 +98,7 @@ def to_dt(date, default_tz=None):
     Non-naive datetime
     """
     if isinstance(date, (int, long)):
-        return ms_to_datetime(date, mktz())
+        return ms_to_datetime(date, default_tz)
     elif date.tzinfo is None:
         if default_tz is None:
             raise ValueError("Must specify a TimeZone on incoming data")

Diff for: tests/unit/date/test_util.py

@@ -4,6 +4,7 @@
 from datetime import datetime as dt
 from arctic.date import datetime_to_ms, ms_to_datetime, mktz, to_pandas_closed_closed, DateRange, OPEN_OPEN, CLOSED_CLOSED
 from arctic.date._mktz import DEFAULT_TIME_ZONE_NAME
+from arctic.date._util import to_dt
 
 
 @pytest.mark.parametrize('pdt', [
@@ -60,3 +61,28 @@ def test_daterange_closedclosed_no_tz():
                          CLOSED_CLOSED)
     act = to_pandas_closed_closed(date_range)
     assert act == expected
+
+
+def test_to_dt_0():
+    assert to_dt(0) == dt(1970, 1, 1, 1, tzinfo=mktz())
+
+
+def test_to_dt_0_default():
+    assert to_dt(0, mktz('UTC')) == dt(1970, 1, 1, tzinfo=mktz('UTC'))
+
+
+def test_to_dt_dt_no_tz():
+    with pytest.raises(ValueError):
+        assert to_dt(dt(1970, 1, 1)) == dt(1970, 1, 1, tzinfo=mktz())
+
+
+def test_to_dt_dt_no_tz_default():
+    assert to_dt(dt(1970, 1, 1), mktz('UTC')) == dt(1970, 1, 1, tzinfo=mktz('UTC'))
+
+
+def test_to_dt_dt_tz():
+    assert to_dt(dt(1970, 1, 1, tzinfo=mktz('UTC'))) == dt(1970, 1, 1, tzinfo=mktz('UTC'))
+
+
+def test_to_dt_dt_tz_default():
+    assert to_dt(dt(1970, 1, 1, tzinfo=mktz('UTC')), mktz('Europe/London')) == dt(1970, 1, 1, tzinfo=mktz('UTC'))