add UT

src/towncrier/_builder.py

@@ -172,11 +172,12 @@ def find_fragments(
                 orphan_fragment_counter[category] += 1
             if config.fragment_filename_stem_pattern and (
                 not re.fullmatch(
-                    config.fragment_filename_stem_pattern, stem := Path(basename).stem
+                    config.fragment_filename_stem_pattern,
+                    stem := Path(basename).stem.removesuffix(f".{category}"),
                 )
             ):
                 raise ClickException(
-                    f"File name '{stem}' does not match the "
+                    f"File name stem '{stem}' does not match the "
                     f"given pattern, '{config.fragment_filename_stem_pattern}'"
                 )
             full_filename = os.path.join(section_dir, basename)

src/towncrier/test/test_check.py

@@ -515,22 +515,35 @@ def test_invalid_fragment_name(self, runner):
         self.assertEqual(1, result.exit_code, result.output)
         self.assertIn("Invalid news fragment name: feature.125", result.output)
 
-    # @with_isolated_runner
-    # def test_invalid_fragment_name_pattern(self, runner):
-    #     """
-    #     Fails if a news fragment has an invalid name, even if `ignore` is not set in
-    #     the config.
-    #     """
-    #     create_project(
-    #         "pyproject.toml",
-    #         extra_config=r'fragment_filename_stem_pattern = "[A-Z]+-\d+"',
-    #     )
-    #     write(
-    #         "foo/newsfragments/124.feature",
-    #         "This fragment has valid name (control case)",
-    #     )
-    #     commit("add stuff")
-
-    #     result = runner.invoke(towncrier_check, ["--compare-with", "main"])
-    #     self.assertEqual(1, result.exit_code, result.output)
-    #     self.assertIn("Invalid news fragment name: feature.125", result.output)
+    @with_isolated_runner
+    def test_fragment_name_stem_pattern(self, runner):
+        """
+        Fails if a news fragment has an invalid name, even if `ignore` is not set in
+        the config.
+        """
+        create_project(
+            "pyproject.toml",
+            extra_config='fragment_filename_stem_pattern = "\\\\d+"',
+        )
+        write(
+            "foo/newsfragments/AAA.feature",  #
+            "This fragment has an invalid name (should be digits only)",
+        )
+        write(
+            "foo/newsfragments/123.feature",  #
+            "This fragment has a valid name",
+        )
+        commit("add stuff")
+
+        result = runner.invoke(towncrier_check, ["--compare-with", "main"])
+        print(">>>")
+        print(result)
+        self.assertEqual(1, result.exit_code, result.output)
+        self.assertIn(
+            "Error: File name stem 'AAA' does not match the given pattern, '\\d+'",
+            result.output,
+        )
+        self.assertNotIn(
+            "Error: File name stem '123' does not match the given pattern, '\\d+'",
+            result.output,
+        )