Checking flash messages in flask application nose tests

The method of testing flashes with session['_flashes'] didn't work for me, because session object simply doesn't have '_flashes' attribute in my case:

with client.session_transaction() as session:    flash_message = dict(session['_flashes']).get('warning')

KeyError: '_flashes'

It might be because most recent version of flask and other packages I use with Python 3.6.4 may work differently, I honestly don't know...

What worked for me is a simple and straightforward:

def test_flash(self):    # attempt login with wrong credentials    response = self.client.post('/authenticate/', data={        'email': 'bla@gmail.com',        'password': '1234'    }, follow_redirects=True)    self.assertTrue(re.search('Invalid username or password',                    response.get_data(as_text=True)))

In my case the flash message was 'Invalid user name or password'.

I think it's also easier to read. Hope it helps those who encountered a similar issue

Here's a sample test that asserts an expected flash message is present. It is based on the method described here:

def test_should_flash_warning_message_when_no_record_found(self):    # Arrange    client = app.test_client()    # Assume    url = '/records/'    expected_flash_message = 'no record found'    # Act    response = client.get(url)    with client.session_transaction() as session:        flash_message = dict(session['_flashes']).get('warning')    # Assert    self.assertEqual(response.status_code, 200, response.data)    self.assertIsNotNone(flash_message, session['_flashes'])    self.assertEqual(flash_message, expected_flash_message)

Note: session['_flashes'] will be a list of tuples. Something like this:

[(u'warning', u'no records'), (u'foo', u'Another flash message.')]