Add tests for ResultSet.

tests/test_resultset.py

+import unittest
+
+from tweepy.models import ResultSet
+
+class NoIdItem(object): pass
+
+class IdItem(object):
+    def __init__(self, id):
+        self.id = id
+
+ids_fixture = [1, 10, 8, 50, 2, 100, 5]
+
+class TweepyResultSetTests(unittest.TestCase):
+    def setUp(self):
+        self.results = ResultSet()
+        for i in ids_fixture:
+            self.results.append(IdItem(i))
+            self.results.append(NoIdItem())
+
+    def testids(self):
+        ids = self.results.ids()
+        self.assertListEqual(ids, ids_fixture)
+
+    def testmaxid(self):
+        self.assertEqual(self.results.max_id, 100)
+
+    def testsinceid(self):
+        self.assertEqual(self.results.since_id, 1)
+