1# Copyright 2013 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 unittest
6
7from metrics import cpu
8
9# Testing private method.
10# pylint: disable=W0212
11class CpuMetricTest(unittest.TestCase):
12  def testSubtractCpuStats(self):
13    # The result computed is a ratio of cpu time used to time elapsed.
14    start = {'Browser': {'CpuProcessTime': 0, 'TotalTime': 0}}
15    end = {'Browser': {'CpuProcessTime': 5, 'TotalTime': 20}}
16    self.assertEqual({'Browser': 0.25}, cpu._SubtractCpuStats(end, start))
17
18    # An error is thrown if the args are called in the wrong order.
19    self.assertRaises(AssertionError, cpu._SubtractCpuStats, start, end)
20
21    # An error is thrown if there's a process type in end that's not in start.
22    end['Renderer'] = {'CpuProcessTime': 2, 'TotalTime': 20}
23    self.assertRaises(AssertionError, cpu._SubtractCpuStats, end, start)
24
25    # A process type will be ignored if there's an empty dict for start or end.
26    start['Renderer'] = {}
27    self.assertEqual({'Browser': 0.25}, cpu._SubtractCpuStats(end, start))
28
29    # Results for multiple process types can be computed.
30    start['Renderer'] = {'CpuProcessTime': 0, 'TotalTime': 0}
31    self.assertEqual({'Browser': 0.25, 'Renderer': 0.1},
32                     cpu._SubtractCpuStats(end, start))
33
34    # Test 32-bit overflow.
35    start = {'Browser': {'CpuProcessTime': 0, 'TotalTime': 2**32 - 20}}
36    end = {'Browser': {'CpuProcessTime': 5, 'TotalTime': 20}}
37    self.assertEqual({'Browser': 0.125}, cpu._SubtractCpuStats(end, start))
38    self.assertRaises(AssertionError, cpu._SubtractCpuStats, start, end)
39
40