Django admin m2m management

admin.py

from django.contrib import admin
from app1.models import *

class MembershipInline(admin.TabularInline):
    model = Membership
    extra = 1
class PersonAdmin(admin.ModelAdmin): 
    inlines = (MembershipInline,) 
class GroupAdmin(admin.ModelAdmin): 
    inlines = (MembershipInline,)

admin.site.register(Person, PersonAdmin)
admin.site.register(Group, GroupAdmin)

models.py

from django.db import models

class Person(models.Model):
    name = models.CharField(max_length=128)
class Group(models.Model):
    name = models.CharField(max_length=128)
    members = models.ManyToManyField(Person, through='Membership')
class Membership(models.Model): 
    person = models.ForeignKey(Person) 
    group = models.ForeignKey(Group) 
    date_joined = models.DateField() 
    invite_reason = models.CharField(max_length=64)

tests.py

import unittest
from datetime import datetime
from django.test.client import Client
from app1.models import *

class ModelsTestCase(unittest.TestCase):
    def setUp(self):
        self.p1 = Person.objects.create(name="qingfeng")
        self.g1 = Group.objects.create(name="python")
        self.m1 = Membership.objects.create(person=self.p1,group=self.g1,date_joined=datetime.now())
        
        self.c = Client()
        
    def testStr(self):
        self.assertEquals(str(self.p1),"qingfeng")
        self.assertEquals(str(self.g1),"python")

    def testUrl(self):
        response = self.c.get("/hello/")
        self.assertEquals(response.content,"Hello Jython And Django!")
        self.assertEquals(response.status_code,200)

urls.py

from django.conf.urls.defaults import *
from django.contrib import admin

admin.autodiscover()

urlpatterns = patterns('',
    # Example:
    # (r'^mytrunk/', include('mytrunk.foo.urls')),

    # Uncomment this for admin:
     ('^admin/(.*)', admin.site.root),
)