fix: unit test book

book/tests.py

 from django.test import TestCase
+from django.utils import timezone
+from django.core.exceptions import ValidationError
 
-# Create your tests here.
+from .models import Category, Book
+
+
+class CategoryModelTest(TestCase):
+
+    def setUp(self):
+        self.category = Category.objects.create(name="Test Category")
+
+    def test_category_creation(self):
+        self.assertEqual(self.category.name, "Test Category")
+
+    def test_category_update(self):
+        self.category.name = "Test Category Update"
+        self.category.save()
+        self.assertEqual(self.category.name, "Test Category Update")
+
+    def test_delete_category(self):
+        category = Category.objects.create(name="Test Delete Category")
+        category.delete()
+        with self.assertRaises(Category.DoesNotExist):
+            Category.objects.get(id=category.id)
+
+
+class BookModelTest(TestCase):
+
+    def setUp(self):
+        self.category = Category.objects.create(name="Test Category")
+        self.book = Book.objects.create(
+            title="Test Book",
+            author="Test Author",
+            publish_date=timezone.now(),
+            rating=3,
+            isbn="1234567890123",
+            category=self.category,
+        )
+
+    def test_book_creation(self):
+        self.assertEqual(self.book.title, "Test Book")
+        self.assertEqual(self.book.author, "Test Author")
+        self.assertEqual(self.book.rating, 3)
+        self.assertEqual(self.book.isbn, "1234567890123")
+        self.assertEqual(self.book.category, self.category)
+
+    def test_book_update(self):
+        self.book.title = "Test Book Update"
+        self.book.save()
+        self.assertEqual(self.book.title, "Test Book Update")
+
+    def test_delete_book(self):
+        book = Book.objects.create(
+            title="Test Book 2",
+            author="Test Author 2",
+            publish_date=timezone.now(),
+            rating=3,
+            isbn="2234567890123",
+        )
+        book.delete()
+
+        with self.assertRaises(Book.DoesNotExist):
+            Book.objects.get(id=book.id)