How to test a helper Grok view that makes a redirect - testing

Question

I have a content type that needs to be modified in some way after calling a helper Grok view that checks some condition, makes some changes, sets a message and redirects to the original object.
my helper view only has a render method and I want to write some tests for it but I have no idea how to handle this.
I would like to check for an error message when some condition is not met, and for an info message when everything goes fine.
my code looks like this:
class MyHelperView(grok.View):
grok.context(IMyType)
grok.layer(IMyLayer)
grok.name('helper-view')
grok.require('my.permission')
def render(self):
variable = self.request.form.get('variable', None)
if not variable:
msg = _(u'Required input is missing.')
api.portal.show_message(message=msg, request=self.request, type='error')
else:
do_something()
msg = _(u'Information processed.')
api.portal.show_message(message=msg, request=self.request)
self.request.response.redirect(self.context.absolute_url())
when I call the view obviously I ended with a None object, as the view returns nothing. I don't know where to look for messages... request? response? any hint?

Answer 1

I would avoid using transaction commits in test code. The test framework is specifically designed to roll back the transactions at the end of each test. Your setUp override goes against this.
To check status messages in a unit test you should be able to do something like:
from Products.statusmessages.interfaces import IStatusMessage
IStatusMessage(request).show()
This is an adapter that adapts the request.

Answer 2

I ended up with test with a layer based on FunctionalTesting:
....
from plone.app.testing import TEST_USER_NAME
from plone.app.testing import TEST_USER_PASSWORD
from plone.testing.z2 import Browser
....
import transaction
...
class HelperViewTestCase(unittest.TestCase):
layer = FUNCTIONAL_TESTING
def setUp(self):
self.app = self.layer['app']
self.portal = self.layer['portal']
self.request = self.layer['request']
directlyProvides(self.request, IMyLayer)
with api.env.adopt_roles(['Manager']):
self.foo = api.content.create(self.portal, 'MyType', 'foo')
transaction.commit()
def test_response(self):
browser = Browser(self.app)
browser.handleErrors = False
browser.addHeader(
'Authorization',
'Basic {0}:{1}'.format(TEST_USER_NAME, TEST_USER_PASSWORD)
)
browser.open(self.foo.absolute_url())
browser.getControl('Do Something').click()
self.assertIn(
'Required input is missing.', browser.contents)
two things you need to check that make me spent some time debugging:
you must use transaction.commit() to reflect object creation on the ZODB
you must add an authorization header before trying to open the page
everything else is working.