Add test for configure_debug_logging

Since we can't directly test it

src/ocrmypdf/_sync.py

@@ -302,7 +302,7 @@ def exec_concurrent(context: PdfContext):
     copy_final(pdf, options.output_file, context)
 
 
-def configure_debug_logging(log_filename, prefix: str = ''):
+def configure_debug_logging(log_filename: Path, prefix: str = ''):
     """
     Create a debug log file at a specified location.
 
@@ -340,7 +340,9 @@ def run_pipeline(options, *, plugin_manager, api=False):
         # Debug log for command line interface only with verbose output
         # See https://github.com/pytest-dev/pytest/issues/5502 for why we skip this
         # when pytest is running
-        debug_log_handler = configure_debug_logging(Path(work_folder) / "debug.log")
+        debug_log_handler = configure_debug_logging(
+            Path(work_folder) / "debug.log"
+        )  # pragma: no cover
 
     pikepdf_enable_mmap()
 

tests/test_logging.py

@@ -0,0 +1,21 @@
+# © 2021 James R. Barlow: github.com/jbarlow83
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import logging
+
+import pytest
+
+from ocrmypdf._sync import configure_debug_logging
+
+
+def test_debug_logging(tmp_path):
+    # Just exercise the debug logger but don't validate it
+    # See https://github.com/pytest-dev/pytest/issues/5502 for pytest logging quirks
+    prefix = 'test_debug_logging'
+    log = logging.getLogger(prefix)
+    handler = configure_debug_logging(tmp_path, prefix)
+    log.info("test message")
+    log.removeHandler(handler)