sample.py

from django import models
from django.test import TestCase

class Person(models.Model):
    first_name = models.CharField(max_length=30)  
    last_name = models.CharField(max_length=30, null=True)  
    age = models.PositiveIntegerField()
    
    def __str__(self):
        return '{} {}'.format(self.first_name, self.last_name)
    
    def save(self, *args, **kwargs):
        if not self.last_name:
            self.last_name = "N/A"
        super(self).save(*args, **kwargs)
  

class PersonTestCase(TestCase):
    def test_should_return_attributes(self):
        self.assertTrue(hasattr(Person, 'first_name'))
        self.assertTrue(hasattr(Person, 'last_name'))
        self.assertTrue(hasattr(Person, 'age'))   
    
    def test_should_create_item(self):
        person = Person.objects.create(first_name='Moacir', last_name='Moda', age=27)
        self.assertIsNotNone(person)
    
    def test_should_assert_methods(self):
        person = Person.objects.create(first_name='Moacir', age=27)
        self.assertIsEqual(person.last_name, 'N/A')
        self.assertIsEqual(str(person), 'Moacir N/A')