test: ☑️ add Python unit test

subsetter_tool.py

@@ -48,8 +48,15 @@ def write_subset_font(
     fonttools_subsetter = subset.Subsetter(options)
     fonttools_subsetter.populate(text=text)
     fonttools_subsetter.subset(font)
-    subset.save_font(font, output_path, options)
+    try:
+        subset.save_font(font, output_path, options)
+    except PermissionError:
+        message = f"\n[ Error ] Unable to write font file `{output_path}`.  Check the "
+        "path exists with write permissions."
+        eprint(message)
+        raise PermissionError(message)
     print("Wrote {} subset to {}".format(format, str(output_path)))
+
     return str(output_path)
 
 
@@ -63,6 +70,8 @@ def write_subset_font_file_for_format(font_file_path_str: str, text: str, hash:
             )
         except FileNotFoundError:
             sys.exit(1)
+        except PermissionError:
+            sys.exit(1)
 
         return subset_file_path
 

tests/test_subsetter_tool.py

@@ -1,4 +1,6 @@
 from pathlib import Path
+import os
+import stat
 import unittest
 
 from subsetter_tool import get_subset_font_path, write_subset_font
@@ -20,7 +22,7 @@ def test_get_subset_font_path_returns_expected_output_for_valid_input(self):
         expected = Path("league-spartan-v11-latin-600__subset_5fba6996.ttf")
         self.assertEqual(result, expected)
 
-    def test_write_subset_font_returns_expected_result(self):
+    def test_write_subset_font_returns_expected_result_for_woff2(self):
         # arrange
         input_path = Path(
             "./fixtures/league-spartan-v11-latin/league-spartan-v11-latin-600.woff2"
@@ -36,17 +38,51 @@ def test_write_subset_font_returns_expected_result(self):
         expected = "league-spartan-v11-latin-600__subset_9e5cab01.woff2"
         self.assertEqual(result, expected)
 
+    def test_write_subset_font_returns_expected_result_for_ttf(self):
+        # arrange
+        input_path = Path(
+            "./fixtures/league-spartan-v11-latin/league-spartan-v11-latin-600.ttf"
+        )
+        text = "Lorem ipsum dolor sit amet"
+        hash = "9e5cab01"
+        format = "ttf"
+
+        # act
+        result = write_subset_font(input_path, text, hash, format)
+
+        # assert
+        expected = "league-spartan-v11-latin-600__subset_9e5cab01.ttf"
+        self.assertEqual(result, expected)
+
     def test_write_subset_font_returns_exception_when_input_path_does_not_exist(self):
         # arrange
         input_path = Path("./fixtures/does-not-exist.ttf")
         text = "Lorem ipsum dolor sit amet"
         hash = "9e5cab01"
-        format = "woff2"
+        format = "ttf"
 
         # act/assert
         with self.assertRaises(FileNotFoundError):
             write_subset_font(input_path, text, hash, format)
 
+    def test_write_subset_font_returns_exception_when_output_is_not_writable(self):
+        # arrange
+        input_path = Path(
+            "./fixtures/league-spartan-v11-latin/league-spartan-v11-latin-700.ttf"
+        )
+        text = "Lorem ipsum dolor sit amet"
+        hash = "9e5cab01"
+        format = "ttf"
+
+        output_path = Path("./league-spartan-v11-latin-700__subset_9e5cab01.ttf")
+        output_path.touch()
+        os.chmod(output_path, stat.S_IRUSR)
+
+        # act/assert
+        with self.assertRaises(PermissionError):
+            write_subset_font(input_path, text, hash, format)
+        os.chmod(output_path, stat.S_IWUSR)
+
 
 if __name__ == "__main__":
     unittest.main()