test: ✅ test dictConfig external reference support

Author: rubensa

tests/test_dictconfig.py

@@ -0,0 +1,80 @@
+### IMPORTS
+### ============================================================================
+## Future
+from __future__ import annotations
+
+## Standard Library
+from dataclasses import dataclass
+import io
+import json
+import logging
+import logging.config
+from typing import Any, Generator
+
+## Installed
+import pytest
+
+### SETUP
+### ============================================================================
+_LOGGER_COUNT = 0
+EXT_VAL = 999
+
+LOGGING_CONFIG = {
+    "version": 1,
+    "disable_existing_loggers": False,
+    "formatters": {
+        "default": {
+            "()": "pythonjsonlogger.json.JsonFormatter",
+            "static_fields": {"ext-val": "ext://tests.test_dictconfig.EXT_VAL"},
+        }
+    },
+    "handlers": {
+        "default": {
+            "level": "DEBUG",
+            "formatter": "default",
+            "class": "logging.StreamHandler",
+            "stream": "ext://sys.stdout",  # Default is stderr
+        },
+    },
+    "loggers": {
+        "": {"handlers": ["default"], "level": "WARNING", "propagate": False},  # root logger
+    },
+}
+
+
+@dataclass
+class LoggingEnvironment:
+    logger: logging.Logger
+    buffer: io.StringIO
+
+    def load_json(self) -> Any:
+        return json.loads(self.buffer.getvalue())
+
+
+@pytest.fixture
+def env() -> Generator[LoggingEnvironment, None, None]:
+    global _LOGGER_COUNT  # pylint: disable=global-statement
+    _LOGGER_COUNT += 1
+    logging.config.dictConfig(LOGGING_CONFIG)
+    default_formatter = logging.root.handlers[0].formatter
+    logger = logging.getLogger(f"pythonjsonlogger.tests.{_LOGGER_COUNT}")
+    logger.setLevel(logging.DEBUG)
+    buffer = io.StringIO()
+    handler = logging.StreamHandler(buffer)
+    handler.setFormatter(default_formatter)
+    logger.addHandler(handler)
+    yield LoggingEnvironment(logger=logger, buffer=buffer)
+    logger.removeHandler(handler)
+    logger.setLevel(logging.NOTSET)
+    buffer.close()
+    return
+
+
+### TESTS
+### ============================================================================
+def test_external_reference_support(env: LoggingEnvironment):
+    env.logger.info("hello")
+    log_json = env.load_json()
+
+    assert log_json["ext-val"] == EXT_VAL
+    return