test(json_decoder): regression test for simplejson encoding-kwarg tolerance (#15)

Guards the e49c9cb fix that swallows simplejson's obsolete encoding=
kwarg (injected by requests via simplejson on Python 3.9+, rejected by
stdlib json.JSONDecoder). The fix was untested until now; a live
BfxLendingBot deploy of v6.0.1 (which predates e49c9cb) crashed on init
with this exact TypeError, motivating a v6.0.2 release plus this guard.

Co-authored-by: cloudingenium-automation[bot] <cloudingenium-automation[bot]@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: cloudingenium-automation[bot]

tests/test_json_decoder.py

@@ -55,3 +55,12 @@ def test_mixed_content(self):
             '{"orderId": 123, "items": [1, 2, 3]}', cls=JSONDecoder
         )
         assert result == {"order_id": 123, "items": [1, 2, 3]}
+
+    def test_tolerates_simplejson_encoding_kwarg(self):
+        # Regression: `requests` routes response.json(cls=JSONDecoder) through
+        # simplejson when python3-simplejson is installed, and simplejson.loads
+        # injects an obsolete `encoding=` kwarg that stdlib json.JSONDecoder
+        # rejects on Python 3.9+ (TypeError). The decoder must swallow it.
+        # Without kwargs.pop("encoding", ...) constructing this raises TypeError.
+        decoder = JSONDecoder(encoding="utf-8")
+        assert decoder.decode('{"firstName": "John"}') == {"first_name": "John"}