Testing python methods that call class methods

Question

I have a very simple method:

Class Team(models.Model):
    def sides(self):
      return SideNames.objects.filter(team=self)

SideNames is another model defined in the same file as Team,

Which when I try and test:

self.assertEquals(len(t.sides()), 2)

I get the following error:

return SideNames.objects.filter(team=self)

AttributeError: 'NoneType' object has no attribute 'objects'

but if I change the test to be

self.assertEquals(len(SideNames.objects.filter(team=t)), 2)

Then I don't get the error. What's the difference between calling SideNames.objects.filter from the test itself and calling the actual method?

For reference, here are the 2 classes in their entirety.

class Team(models.Model):
    """The model for a football team."""

    class Admin:
            pass

    def __unicode__(self):
            return u'%s' % self.name

    def is_player(self, player):
            """Checks to see if 'player' is a member if this team. Returns True if they are, or False otherwise."""

            try:
                    teamPlayer = TeamPlayers.objects.get(player=player, team=self)
                    return True
            except ObjectDoesNotExist:
                    return False

    def sides(self):
            """Return the side names for this team"""
            return SideNames.objects.filter(team=self)

    def updateSides(self, side_a, side_b):
            """Update the side names"""
            names = SideNames.objects.filter(team=self);

            a = SideNames.objects.get(name = names[0].name)
            a.name = side_a
            a.save()

            b = SideNames.objects.get(name = names[1].name)
            b.name = side_b
            b.save()

    name = models.CharField("Team Name", max_length=255)
    organiser = models.ForeignKey(User)

class SideNames(models.Model):
    """Holds the names of the sides for each team"""

    class Admin:
            pass

    def __unicode__(self):
            """Pretty print the SideNames object"""
            return self.name

    team = models.ForeignKey(Team)
    name = models.CharField(max_length=128)

Answer 1

In the module that defines the test, you're importing the name SideNames from some other module. In the module where that sides method is defined, the name SideNames is not defined or imported.

Answer 2

By any chance, does your test do something like this:

from myapp import models

...

models.SideNames = None

since that's the only explanation I can think of for why SideNames should be None in the context of that method.

As an aside, the method itself is pointless, as backwards relations are automatically provided by Django, so you could just call t.sidenames_set.all().