Address @cyli's two points -- a test for ordering, and documentation of when None is returned.

Author: radix

effect/test_testing.py

@@ -284,7 +284,7 @@ class SequenceDispatcherTests(TestCase):
 
     def test_mismatch(self):
         """
-        When an intent isn't expected, a :obj:`None` is returned.
+        When an intent isn't expected, a None is returned.
         """
         d = SequenceDispatcher([('foo', lambda i: 1 / 0)])
         self.assertEqual(d('hello'), None)
@@ -307,3 +307,11 @@ def test_ran_out(self):
         """When there are no more items left, None is returned."""
         d = SequenceDispatcher([])
         self.assertEqual(d('foo'), None)
+
+    def test_out_of_order(self):
+        """Order of items in the sequence matters."""
+        d = SequenceDispatcher([
+            ('bar', lambda i: ('performbar', i)),
+            ('foo', lambda i: ('performfoo', i)),
+        ])
+        self.assertEqual(d('foo'), None)

effect/testing.py

@@ -258,6 +258,10 @@ class SequenceDispatcher(object):
             (MyIntent('a'), lambda i: 'my-intent-result'),
             (OtherIntent('b'), lambda i: 'other-intent-result')
         ])
+
+    :obj:`None` is returned if the next intent in the sequence is not equal to
+    the intent being performed, or if there are no more items left in the
+    sequence.
     """
     def __init__(self, sequence):
         """:param list sequence: Sequence of (intent, fn)."""