Fix weeks property for negative Period instances

Author: sdispater

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Change Log
 
+## [Unreleased]
+
+### Fixed
+
+- Fixed the `weeks` property for negative `Period` instances.
+
+
 ## [2.0.1] - 2018-05-10
 
 ### Fixed

pendulum/period.py

@@ -144,7 +144,7 @@ def months(self):
 
     @property
     def weeks(self):
-        return self._delta.days // 7
+        return abs(self._delta.days) // 7 * self._sign(self._delta.days)
 
     @property
     def days(self):

tests/period/test_add_subtract.py

@@ -28,3 +28,25 @@ def test_dst_subtract():
     new_start = end - period
 
     assert new_start == start
+
+
+def test_naive_subtract():
+    start = pendulum.naive(2013, 3, 31, 1, 30)
+    end = start.add(hours=1)
+    period = end - start
+    new_end = start + period
+
+    assert new_end == end
+
+
+def test_negative_difference_subtract():
+    start = pendulum.datetime(2018, 5, 28, 12, 34, 56, 123456)
+    end = pendulum.datetime(2018, 1, 1)
+
+    print((start - end).in_words())
+
+    period = end - start
+    print(period.in_words())
+    new_end = start + period
+
+    assert new_end == end