1 # Copyright (c) 2012 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.
5 from telemetry.page import page_test
8 class MeasurementFailure(page_test.Failure):
9 """Exception that can be thrown from MeasurePage to indicate an undesired but
10 designed-for problem."""
13 class PageMeasurement(page_test.PageTest):
14 """Glue code for running a measurement across a set of pages.
16 To use this, subclass from the measurement and override MeasurePage. For
19 class BodyChildElementMeasurement(PageMeasurement):
20 def MeasurePage(self, page, tab, results):
21 body_child_count = tab.EvaluateJavaScript(
22 'document.body.children.length')
23 results.Add('body_children', 'count', body_child_count)
25 if __name__ == '__main__':
26 page_measurement.Main(BodyChildElementMeasurement())
28 To add test-specific options:
30 class BodyChildElementMeasurement(PageMeasurement):
31 def AddCommandLineArgs(parser):
32 parser.add_option('--element', action='store', default='body')
34 def MeasurePage(self, page, tab, results):
35 body_child_count = tab.EvaluateJavaScript(
36 'document.querySelector('%s').children.length')
37 results.Add('children', 'count', child_count)
40 action_name_to_run='',
41 needs_browser_restart_after_each_page=False,
42 discard_first_result=False,
43 clear_cache_before_each_run=False):
44 super(PageMeasurement, self).__init__(
46 needs_browser_restart_after_each_page,
48 clear_cache_before_each_run)
50 def ValidatePage(self, page, tab, results):
51 results.WillMeasurePage(page)
53 self.MeasurePage(page, tab, results)
55 results.DidMeasurePage()
58 def results_are_the_same_on_every_page(self):
59 """By default, measurements are assumed to output the same values for every
60 page. This allows incremental output, for example in CSV. If, however, the
61 measurement discovers what values it can report as it goes, and those values
62 may vary from page to page, you need to override this function and return
63 False. Output will not appear in this mode until the entire pageset has
67 def MeasurePage(self, page, tab, results):
68 """Override to actually measure the page's performance.
70 page is a page_set.Page
71 tab is an instance of telemetry.core.Tab
73 Should call results.Add(name, units, value) for each result, or raise an
74 exception on failure. The name and units of each Add() call must be
75 the same across all iterations. The name 'url' must not be used.
77 Prefer field names that are in accordance with python variable style. E.g.
82 def MeasurePage(self, page, tab, results):
83 res = tab.EvaluateJavaScript('2+2')
85 raise Exception('Oh, wow.')
86 results.Add('two_plus_two', 'count', res)
88 raise NotImplementedError()