Preserving query count

Given you want to read or create many items instead of one, you need to make sure that the number of queries stays constant.

In Launchpad this can be done by using lp.testing.record_two_runs, as outlined in the following example:

def test_view_query_count(self):
    # Test that the view bulk loads artifacts.
    person = self.factory.makePerson()
    pillarperson = PillarPerson(self.pillar, person)
    recorder1, recorder2 = record_two_runs(
        tested_method=lambda: create_initialized_view(pillarperson, '+index'),
        item_creator=lambda: self.makeArtifactGrantee(person, True, True, True, False),
        first_round_number=5,
        login_method=lambda: login_person(self.owner))
    self.assertThat(recorder2, HasQueryCount.byEquality(recorder1))

For further information, please have a look at record_two_runs’ docstring.