Improve tests for slicing

tests/test_offline.py

@@ -313,6 +313,17 @@ class TestOfflineTracks(unittest.TestCase):
         assert 5 == len(track_selection)
         track_selection_2 = tracks[1:3]
         assert 2 == len(track_selection_2)
+        for _slice in [
+            slice(0, 0),
+            slice(0, 1),
+            slice(0, 2),
+            slice(1, 5),
+            slice(3, -2)
+        ]:
+            self.assertListEqual(
+                list(tracks.E[:,0][_slice]),
+                list(tracks[_slice].E[:,0])
+            )
 
 
 class TestOfflineTrack(unittest.TestCase):