Feature: Add list unread books command

samples/book-app-project/README.md

@@ -3,7 +3,7 @@
 *(This README is intentionally rough so you can improve it with GitHub Copilot CLI)*
 
 A Python app for managing books you have or want to read.
-It can add, remove, and list books. Also mark them as read.
+It can add, remove, and list books, including only unread books. Also mark them as read.
 
 ---
 
@@ -29,6 +29,7 @@ It can add, remove, and list books. Also mark them as read.
 
 ```bash
 python book_app.py list
+python book_app.py list unread
 python book_app.py add
 python book_app.py find
 python book_app.py remove

samples/book-app-project/book_app.py

@@ -26,6 +26,11 @@ def handle_list():
     show_books(books)
 
 
+def handle_list_unread():
+    books = collection.get_unread_books()
+    show_books(books)
+
+
 def handle_add():
     print("\nAdd a New Book\n")
 
@@ -65,6 +70,7 @@ def show_help():
 
 Commands:
   list     - Show all books
+  list unread - Show unread books
   add      - Add a new book
   remove   - Remove a book by title
   find     - Find books by author
@@ -79,7 +85,9 @@ def main():
 
     command = sys.argv[1].lower()
 
-    if command == "list":
+    if command == "list" and len(sys.argv) > 2 and sys.argv[2].lower() == "unread":
+        handle_list_unread()
+    elif command == "list":
         handle_list()
     elif command == "add":
         handle_add()

samples/book-app-project/books.py

@@ -44,6 +44,9 @@ 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 [book for book in self.books if not book.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_book_app.py

@@ -0,0 +1,60 @@
+import os
+import sys
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+import book_app
+import books
+from books import BookCollection
+
+
+@pytest.fixture
+def collection(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> BookCollection:
+    data_file = tmp_path / "data.json"
+    data_file.write_text("[]")
+    monkeypatch.setattr(books, "DATA_FILE", str(data_file))
+    test_collection = BookCollection()
+    monkeypatch.setattr(book_app, "collection", test_collection)
+    return test_collection
+
+
+def test_list_unread_command_displays_unread_books_only(
+    collection: BookCollection,
+    monkeypatch: pytest.MonkeyPatch,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    collection.add_book("Dune", "Frank Herbert", 1965)
+    collection.add_book("1984", "George Orwell", 1949)
+    collection.mark_as_read("1984")
+    monkeypatch.setattr(sys, "argv", ["book_app.py", "list", "unread"])
+
+    book_app.main()
+
+    output = capsys.readouterr().out
+    assert "Dune by Frank Herbert (1965)" in output
+    assert "1984 by George Orwell" not in output
+
+
+def test_list_unread_command_reports_no_books_when_none_are_unread(
+    collection: BookCollection,
+    monkeypatch: pytest.MonkeyPatch,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    monkeypatch.setattr(sys, "argv", ["book_app.py", "list", "unread"])
+
+    book_app.main()
+
+    assert "No books found." in capsys.readouterr().out
+
+
+def test_help_includes_list_unread_command(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+) -> None:
+    monkeypatch.setattr(sys, "argv", ["book_app.py", "help"])
+
+    book_app.main()
+
+    assert "list unread - Show unread books" in capsys.readouterr().out

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

@@ -26,6 +26,53 @@ def test_add_book():
     assert book.year == 1949
     assert book.read is False
 
+
+def test_get_unread_books_returns_only_unread_books():
+    collection = BookCollection()
+    collection.add_book("Dune", "Frank Herbert", 1965)
+    collection.add_book("1984", "George Orwell", 1949)
+    collection.mark_as_read("1984")
+
+    assert [book.title for book in collection.get_unread_books()] == ["Dune"]
+
+
+def test_get_unread_books_preserves_order():
+    collection = BookCollection()
+    collection.add_book("Dune", "Frank Herbert", 1965)
+    collection.add_book("1984", "George Orwell", 1949)
+    collection.add_book("The Hobbit", "J.R.R. Tolkien", 1937)
+    collection.mark_as_read("1984")
+
+    assert [book.title for book in collection.get_unread_books()] == [
+        "Dune",
+        "The Hobbit",
+    ]
+
+
+def test_get_unread_books_returns_empty_list_for_empty_collection():
+    collection = BookCollection()
+
+    assert collection.get_unread_books() == []
+
+
+def test_get_unread_books_returns_empty_list_when_all_books_are_read():
+    collection = BookCollection()
+    collection.add_book("1984", "George Orwell", 1949)
+    collection.mark_as_read("1984")
+
+    assert collection.get_unread_books() == []
+
+
+def test_get_unread_books_returns_separate_list():
+    collection = BookCollection()
+    collection.add_book("Dune", "Frank Herbert", 1965)
+
+    unread_books = collection.get_unread_books()
+    unread_books.clear()
+
+    assert len(collection.list_books()) == 1
+
+
 def test_mark_book_as_read():
     collection = BookCollection()
     collection.add_book("Dune", "Frank Herbert", 1965)