trackdb: Give stacks an easy way to queue up tracks

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

trackdb/stack.py

@@ -34,3 +34,7 @@ class TagStack:
             self.tags.remove(tag)
         self.tags.insert(0, tag)
         tag.stacked()
+
+    def queue(self, track):
+        track.add_to_playlist("Up Next")
+        self.push(tags.User["Up Next"])

trackdb/test_stack.py

@@ -7,10 +7,14 @@ import unittest
 class FakeTrack:
     def __init__(self, n):
         self.n = n
+        self.length = n
 
     def add_to_playlist(self, name):
         tags.User.add(name, self)
 
+    def remove_from_playlist(self, name):
+        tags.User[name].remove_track(self)
+
 class TestTagStack(unittest.TestCase):
     def tearDown(self):
         tags.reset()
@@ -77,3 +81,11 @@ class TestTagStack(unittest.TestCase):
         self.assertEqual(s.tags, [ t1, t2 ])
         s.push(tags.User["Collection"])
         self.assertEqual(s.tags, [ ])
+
+    def test_tag_stack_queue(self):
+        s = stack.TagStack()
+        s.queue(FakeTrack(1))
+
+        self.assertEqual(s.tags, [ tags.User["Up Next"] ])
+        self.assertEqual(s.next().n, 1)
+        self.assertEqual(tags.User["Up Next"].tracks, [ ])