1# Copyright 2014 The Chromium Authors. All rights reserved.
2# Use of this source code is governed by a BSD-style license that can be
3# found in the LICENSE file.
4
5import math
6import unittest
7
8import math_utils
9
10
11class MathUtilsTest(unittest.TestCase):
12  """Tests for mathematical utility functions."""
13
14  def testTruncatedMeanRaisesError(self):
15    """TruncatedMean should raise an error when passed an empty list."""
16    with self.assertRaises(TypeError):
17      math_utils.TruncatedMean([], 0)
18
19  def testMeanSingleNum(self):
20    """Tests the Mean function with a single number."""
21    self.assertEqual(3.0, math_utils.Mean([3]))
22
23  def testMeanShortList(self):
24    """Tests the Mean function with a short list."""
25    self.assertEqual(0.5, math_utils.Mean([-3, 0, 1, 4]))
26
27  def testMeanCompareAlternateImplementation(self):
28    """Tests Mean by comparing against an alternate implementation."""
29    def AlternateMeanFunction(values):
30      """Simple arithmetic mean function."""
31      return sum(values) / float(len(values))
32    test_values_lists = [[1], [5, 6.5, 1.2, 3], [-3, 0, 1, 4],
33                         [-3, -1, 0.12, 0.752, 3.33, 8, 16, 32, 439]]
34    for values in test_values_lists:
35      self.assertEqual(
36          AlternateMeanFunction(values),
37          math_utils.Mean(values))
38
39  def testRelativeChange(self):
40    """Tests the common cases for calculating relative change."""
41    # The change is relative to the first value, regardless of which is bigger.
42    self.assertEqual(0.5, math_utils.RelativeChange(1.0, 1.5))
43    self.assertEqual(0.5, math_utils.RelativeChange(2.0, 1.0))
44
45  def testRelativeChangeFromZero(self):
46    """Tests what happens when relative change from zero is calculated."""
47    # If the first number is zero, then the result is not a number.
48    self.assertEqual(0, math_utils.RelativeChange(0, 0))
49    self.assertTrue(
50        math.isnan(math_utils.RelativeChange(0, 1)))
51    self.assertTrue(
52        math.isnan(math_utils.RelativeChange(0, -1)))
53
54  def testRelativeChangeWithNegatives(self):
55    """Tests that relative change given is always positive."""
56    self.assertEqual(3.0, math_utils.RelativeChange(-1, 2))
57    self.assertEqual(3.0, math_utils.RelativeChange(1, -2))
58    self.assertEqual(1.0, math_utils.RelativeChange(-1, -2))
59
60
61if __name__ == '__main__':
62  unittest.main()
63