Revert "clean up test"

This reverts commit 66c3af1.

Author: kumaraditya303

Lib/test/test_json/test_dump.py

@@ -66,6 +66,10 @@ def __lt__(self, o):
         self.assertEqual(self.dumps(d, sort_keys=True), '{"1337": "true.dat"}')
 
     def test_mutate_items_during_encode(self):
+        c_make_encoder = getattr(self.json.encoder, 'c_make_encoder', None)
+        if c_make_encoder is None:
+            self.skipTest("c_make_encoder not available")
+
         cache = []
 
         class BadDict(dict):
@@ -80,9 +84,20 @@ def items(self):
         def encode_str(obj):
             if cache:
                 cache.pop().clear()
-            return 'x'
+            return '"x"'
+
+        encoder = c_make_encoder(
+            None, lambda o: "null",
+            encode_str, None,
+            ": ", ", ", False,
+            False, True
+        )
+
+        try:
+            encoder(BadDict(), 0)
+        except (ValueError, RuntimeError):
+            pass
 
-        self.assertEqual(self.dumps(BadDict(), default=encode_str), '{"boom": "x"}')
 
 class TestPyDump(TestDump, PyTest): pass