curds: Add extra playlist next() tests

We want to make sure we get the expected results when calling next() on
empty playlists and with playlists that only have one track.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

curds/playlist/playlist.py

@@ -16,7 +16,11 @@ class Playlist(list):
 
     def next(self):
         max = len(self) - 1
-        if self.random == True:
+        if max == -1:
+            return None
+        elif max == 0:
+            self.current = 0
+        elif self.random == True:
             self.current = (self.current + random.randint(1, max)) % max
         elif self.current < max:
             self.current += 1

curds/playlist/test_playlist.py

@@ -145,3 +145,30 @@ class TestPlaylist(unittest.TestCase):
             track = plist.next()
             self.assertEqual(plist.current, i)
             self.assertEqual(track, tracks[i])
+
+    def test_playlist_next_empty(self):
+        plist = playlist.Playlist("Test Playlist")
+
+        self.assertIsNone(plist.next())
+        self.assertEqual(plist.current, -1)
+        plist.set_loop(True)
+        self.assertIsNone(plist.next())
+        self.assertEqual(plist.current, -1)
+        plist.set_random(True)
+        self.assertIsNone(plist.next())
+        self.assertEqual(plist.current, -1)
+
+    def test_playlist_next_one(self):
+        path  = os.path.join(test_library, "Test Artist 01", "Test Album 1")
+        plist = playlist.Playlist("Test Playlist")
+        track = tags.Track.lookup(os.path.join(path, "01 - Test Track 01.ogg"))
+
+        plist.add(track)
+        self.assertEqual(plist.next(), track)
+        self.assertEqual(plist.current, 0)
+        plist.set_loop(True)
+        self.assertEqual(plist.next(), track)
+        self.assertEqual(plist.current, 0)
+        plist.set_random(True)
+        self.assertEqual(plist.next(), track)
+        self.assertEqual(plist.current, 0)