#30973: Selenium wait_page_loaded waits for wrong page (race condition)
---------------------------------------------+--------------------------
Reporter: Johannes Hoppe | Owner: nobody
Type: Bug | Status: new
Component: Testing framework | Version: master
Severity: Normal | Keywords: selenium
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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Right now
`django.contrib.admin.tests.AdminSeleniumTestCase.wait_page_loaded` waits
for the `body` HTML-tag to be present. It is meant to be executed after a
page reload is triggered, like a form submit.
However, if the test suite is a little faster than our browser (race
condition), we are looking get confirmation for the body tag of the old
page, not the new one.
The safe (and correct) way to wait in selenium for a page to re reloaded
is to wait until the old one is gone and the new one is ready. Preferably
with a context manager like so:
{{{
@contextmanager
def wait_page_loaded(self, timeout=10):
"""
Block until page has started to load.
"""
from selenium.common.exceptions import TimeoutException
from selenium.webdriver.support import expected_conditions as ec
try:
old_page = self.selenium.find_element_by_tag_name('html')
yield
# Wait for the next page to be loaded
self.wait_until(ec.staleness_of(old_page), timeout=timeout)
self.wait_until(
lambda driver:
driver.execute_script('return document.readyState;') ==
'complete',
timeout=timeout
)
except TimeoutException:
# IE7 occasionally returns an error "Internet Explorer cannot
# display the webpage" and doesn't load the next page. We just
# ignore it.
pass
}}}
In some cases we might also want to wait for a site to be ready after a
regular `selenium.get`.
In that case with should have a separate method, like so:
{{{
def wait_page_ready(self, timeout=10):
"""
Block until page has started to load.
"""
self.wait_until(
lambda driver: driver.execute_script('return
document.readyState;') == 'complete',
timeout
)
}}}
This bug currently affects a lot of tests and fails preferably when you
run FireFox but I've seen it on Chrome too.
--
Ticket URL: <https://code.djangoproject.com/ticket/30973>
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