add test that makes sure that the 'AverageLearner' only returns new points

adaptive/tests/test_average_learner.py

+# -*- coding: utf-8 -*-
+
+from ..learner import AverageLearner
+
+
+def test_only_returns_new_points():
+    learner = AverageLearner(lambda x: x, atol=None, rtol=0.01)
+
+    # Only tell it n = 5...10
+    for i in range(5, 10):
+        learner.tell(i, 1)
+
+    learner.tell(0, None)  # This means it shouldn't return 0 anymore
+
+    assert learner.ask(1)[0][0] == 1
+    assert learner.ask(1)[0][0] == 2
+    assert learner.ask(1)[0][0] == 3
+    assert learner.ask(1)[0][0] == 4
+    assert learner.ask(1)[0][0] == 10