Testing for error cases.

Author: mikeckennedy

apps/py/ch09_testing/lib.py

@@ -12,6 +12,9 @@ def __init__(self, name: str = None, price: float = 0.0,
 
 
 def all_guitars(style: Optional[str]) -> List[Guitar]:
+    if style is None or not style.strip():
+        raise ValueError(f"'{style}' is an invalid style.")
+
     style = style.lower()
 
     log(f"Guitars for {style}")

apps/py/ch09_testing/test_lib.py

@@ -1,5 +1,7 @@
 from typing import List
 
+import pytest
+
 import lib
 import pytest_mock
 # noinspection PyUnresolvedReferences
@@ -37,3 +39,8 @@ def test_all_guitars(guitar_data: List[lib.Guitar], mocker: pytest_mock.MockFixt
     types = {g.style for g in guitars}
 
     assert types == {'acoustic', 'electric'}
+
+
+def test_invalid_style():
+    with pytest.raises(ValueError):
+        lib.all_guitars(None)