feat: add list unread books command

- Add get_unread_books() method to BookCollection in books.py
- Add 'unread' command handler in book_app.py
- Update help text with new unread command
- Add 4 test cases covering empty, all unread, some read, and all read scenarios

Author: DanWahlin

samples/book-app-project/book_app.py

@@ -50,6 +50,11 @@ def handle_remove():
     print("\nBook removed if it existed.\n")
 
 
+def handle_list_unread():
+    books = collection.get_unread_books()
+    show_books(books)
+
+
 def handle_find():
     print("\nFind Books by Author\n")
 
@@ -65,6 +70,7 @@ def show_help():
 
 Commands:
   list     - Show all books
+  unread   - Show unread books
   add      - Add a new book
   remove   - Remove a book by title
   find     - Find books by author
@@ -79,6 +85,7 @@ def main():
 
     commands = {
         "list": handle_list,
+        "unread": handle_list_unread,
         "add": handle_add,
         "remove": handle_remove,
         "find": handle_find,

samples/book-app-project/books.py

@@ -44,6 +44,10 @@ def add_book(self, title: str, author: str, year: int) -> Book:
     def list_books(self) -> List[Book]:
         return self.books
 
+    def get_unread_books(self) -> List[Book]:
+        """Return all books that haven't been read yet."""
+        return [b for b in self.books if not b.read]
+
     def find_book_by_title(self, title: str) -> Optional[Book]:
         for book in self.books:
             if book.title.lower() == title.lower():

samples/book-app-project/tests/test_books.py

@@ -51,3 +51,37 @@ def test_remove_book_invalid():
     collection = BookCollection()
     result = collection.remove_book("Nonexistent Book")
     assert result is False
+
+
+def test_get_unread_books_empty_collection():
+    collection = BookCollection()
+    unread = collection.get_unread_books()
+    assert unread == []
+
+
+def test_get_unread_books_all_unread():
+    collection = BookCollection()
+    collection.add_book("1984", "George Orwell", 1949)
+    collection.add_book("Dune", "Frank Herbert", 1965)
+    unread = collection.get_unread_books()
+    assert len(unread) == 2
+
+
+def test_get_unread_books_some_read():
+    collection = BookCollection()
+    collection.add_book("1984", "George Orwell", 1949)
+    collection.add_book("Dune", "Frank Herbert", 1965)
+    collection.mark_as_read("Dune")
+    unread = collection.get_unread_books()
+    assert len(unread) == 1
+    assert unread[0].title == "1984"
+
+
+def test_get_unread_books_all_read():
+    collection = BookCollection()
+    collection.add_book("1984", "George Orwell", 1949)
+    collection.add_book("Dune", "Frank Herbert", 1965)
+    collection.mark_as_read("1984")
+    collection.mark_as_read("Dune")
+    unread = collection.get_unread_books()
+    assert len(unread) == 0