Challenge 1: Write a Model Test — Possible Solution
====================================================================

# catalog/tests.py

from django.test import TestCase
from .models import Author

class AuthorModelTests(TestCase):
    def setUp(self):
        self.author = Author.objects.create(
            name="Octavia E. Butler",
            bio="American science fiction author.",
        )

    def test_author_str_returns_name(self):
        self.assertEqual(str(self.author), "Octavia E. Butler")

    def test_author_was_saved_to_database(self):
        self.assertEqual(Author.objects.count(), 1)
        saved_author = Author.objects.get(pk=self.author.pk)
        self.assertEqual(saved_author.name, "Octavia E. Butler")

WHY THIS WORKS
--------------
- setUp() runs before EACH test method in the class, creating a fresh
  self.author every time — because Django's TestCase rolls back the
  database transaction after every test, test_author_was_saved_to_database
  never sees a leftover author from test_author_str_returns_name (or
  vice versa), even though both tests create an author with the same name.
- self.assertEqual(str(self.author), "Octavia E. Butler") tests the
  model's __str__ method directly — Django's default admin display and
  shell repr both rely on __str__, so testing it directly catches a
  regression before it shows up as a confusing "Author object (1)" in
  the admin.
- test_author_was_saved_to_database double-checks that create() actually
  persisted the object (not just built an unsaved instance) by re-fetching
  it fresh from the database via Author.objects.get(pk=...) rather than
  just inspecting the in-memory self.author object.