Test logger output after configuring logging

#3
https://docs.pytest.org/en/latest/how-to/capture-stdout-stderr.html
https://docs.pytest.org/en/latest/how-to/logging.html

In addition to testing the methods that load the logging configuration,
it can also be useful to test that logger messages have the expected
format. This commit will add tests that output logger messages in
various formats and assert that each output matches the expected format.

As in the tests of the Gunicorn server output, these tests will use the
pytest `capfd` fixture. It is also possible to use the `caplog` fixture,
but I have not had as much success with it.

tests/test_logging_conf.py

@@ -1,3 +1,4 @@
+import datetime
 import os
 from pathlib import Path
 
@@ -138,3 +139,44 @@ def test_configure_logging_tmp_module_no_dict(
         logger.error.assert_called_once_with(
             f"{logger_error_msg}: AttributeError {attribute_error_msg}."
         )
+
+
+class TestLoggingOutput:
+    """Test logger output after configuring logging.
+    ---
+    """
+
+    def test_logging_output_default(self, capfd: pytest.CaptureFixture) -> None:
+        """Test logger output with default format."""
+        logger = logging_conf.logging.getLogger()
+        logging_conf.configure_logging()
+        logger.info("Hello, World!")
+        captured = capfd.readouterr()
+        assert "INFO" in captured.out
+        assert "Hello, World!" in captured.out
+
+    @pytest.mark.parametrize(
+        "log_format,log_level_output", (("gunicorn", "[DEBUG]"), ("verbose", "DEBUG"))
+    )
+    def test_logging_output_custom_format(
+        self,
+        capfd: pytest.CaptureFixture,
+        log_format: str,
+        log_level_output: str,
+        logging_conf_tmp_file_path: Path,
+        monkeypatch: pytest.MonkeyPatch,
+    ) -> None:
+        """Test logger output with custom format."""
+        today = datetime.date.today()
+        logging_conf_file = f"{logging_conf_tmp_file_path}/tmp_log.py"
+        monkeypatch.setenv("LOG_FORMAT", "gunicorn")
+        monkeypatch.setenv("LOG_LEVEL", "debug")
+        logger = logging_conf.logging.getLogger()
+        logging_conf.configure_logging(logging_conf=logging_conf_file)
+        logger.debug("Hello, Customized World!")
+        captured = capfd.readouterr()
+        assert str(today) in captured.out
+        assert log_format not in captured.out
+        assert log_level_output in captured.out
+        assert f"Logging dict config loaded from {logging_conf_file}." in captured.out
+        assert "Hello, Customized World!" in captured.out