Starting a Flask Server from Within Test Code? - python-3.x

Question

I'm working through the Flasky tutorial from Miguel Grinberg's book Flask Web Development 2e and I've run into a snag with the end-to-end testing in Chapter 15. When I try to run the code I get a console message
* Ignoring a call to 'app.run()' that would block the current 'flask' CLI command.
Only call 'app.run()' in an 'if __name__ == "__main__"' guard.
followed by the browser reporting "Firefox cannot establish a connection..." This suggest to me that the test server is not starting.
Here's the code, from pages 231-233 of the book (the file is tests/test_selenium.py):
import threading
import unittest
from selenium import webdriver
from app import create_app, db, fake
from app.models import Role, User
class SeleniumTestCase(unittest.TestCase):
browser = None
#classmethod
def setUpClass(cls) -> None:
try:
cls.browser = webdriver.Firefox()
except Exception as e:
pass
if cls.browser:
cls.app = create_app('testing')
cls.app_context = cls.app.app_context()
cls.app_context.push()
import logging
logger = logging.getLogger('werkzeug')
logger.setLevel('ERROR')
db.create_all()
Role.insert_roles()
fake.users(10)
fake.posts(10)
admin_role = Role.query.filter_by(permissions=0xff).first()
admin = User(email='john#example.com', password='cat', username='john', role=admin_role, confirmed=True)
db.session.add(admin)
db.session.commit()
cls.server_thread = threading.Thread(
target=cls.app.run,
kwargs={
'debug': 'false',
'use_reloader': False,
'use_debugger': False,
'host': '0.0.0.0',
'port': 5000
}
)
cls.server_thread.start()
#classmethod
def tearDownClass(cls) -> None:
if cls.browser:
cls.browser.get('http://localhost:5000/shutdown')
cls.browser.quit()
cls.server_thread.join()
db.drop_all()
db.session.remove()
cls.app_context.pop()
def setUp(self) -> None:
if not self.browser:
self.skipTest('Web browser not available')
def tearDown(self) -> None:
pass
def test_admin_home_page(self):
self.browser.get('http://localhost:5000/') # fails here
self.assertRegex(self.browser.page_source, 'Hello,\s+Stranger!')
self.fail('Finish the test!')
How can I get a test server up and running from within the test code? (I putzed around with Flask-Testing for a few days before giving it up as unmaintained.)
ADDENDUM: Further experimentation has determined that the problem lies in the explicit call to app.run() conflicting with the Flask CLI's implicit call to app.run(), but without the explicit call the test server doesn't start.
I want to run this from the Flask CLI the same as my unit tests. This means I need to find a way to start the test server after the test database is populated, which happens after the test class's code begins to run. The CLI command code is:
#app.cli.command()
#click.argument('test_names', nargs=-1)
def test(coverage, test_names):
"""Run the unit tests"""
import unittest
if test_names:
tests = unittest.TestLoader().loadTestsFromNames(test_names)
else:
tests = unittest.TestLoader().discover('tests')
unittest.TextTestRunner(verbosity=2).run(tests)
so running from __main__ would bypass the tests' load/run sequence.

Answer 1

I found a feasible solution using Timer
import unittest
from threading import Timer
Create two variables on top in your code
timer = None
myapp = None
class ApplicationTest(unittest.TestCase):
Now at the bottom of the file create main method and custom method of timer, I assume startTest as method name
In the main method you can call create_app and put it in global variable and use that myapp variable inside your selenium testing code
unittest.main() will manually trigger your test class and run the test cases one after one, unfortunately the test runs twice, I don't know why
def startTest():
timer.cancel()
unittest.main()
if __name__ == '__main__':
timer = Timer(6.0, startTest)
timer.start()
myapp = create_app()
myapp.run(debug=True, threaded=True)