Inject get_data for testing

axelrod/load_data_.py

@@ -1,6 +1,6 @@
 import pathlib
 import pkgutil
-from typing import Dict, List, Text, Tuple
+from typing import Callable, Dict, List, Optional, Tuple
 
 
 def axl_filename(path: pathlib.Path) -> pathlib.Path:
@@ -20,14 +20,18 @@ def axl_filename(path: pathlib.Path) -> pathlib.Path:
     return axl_path / path
 
 
-def load_file(filename: str, directory: str) -> List[List[str]]:
+def load_file(
+    filename: str,
+    directory: str,
+    get_data: Callable[[str, str], Optional[bytes]] = pkgutil.get_data,
+) -> List[List[str]]:
     """Loads a data file stored in the Axelrod library's data subdirectory,
     likely for parameters for a strategy."""
 
     path = str(pathlib.Path(directory) / filename)
-    data_bytes = pkgutil.get_data(__name__, path)
+    data_bytes = get_data(__name__, path)
     if data_bytes is None:
-        raise FileNotFoundError(path)
+        raise FileNotFoundError(f"Some loader issue for path {path}")
     data = data_bytes.decode("UTF-8", "replace")
 
     rows = []

axelrod/tests/unit/test_load_data.py

@@ -18,5 +18,12 @@ def test_axl_filename(self):
 
     def test_raise_error_if_file_empty(self):
         path = pathlib.Path("not/a/file.py")
-        with self.assertRaisesRegex(FileNotFoundError, str(path)):
+        with self.assertRaises(FileNotFoundError):
             load_file(path, ".")
+
+    def test_raise_error_if_something(self):
+        dirname = os.path.dirname(__file__)
+        path = os.path.join(dirname, "../../strategies/titfortat.py")
+        bad_loader = lambda _, __: None
+        with self.assertRaises(FileNotFoundError):
+            load_file(path, ".", bad_loader)