Add test for raw copy memleak

tests/test_raw.py

@@ -1,5 +1,7 @@
 import operator
+import subprocess
 import sys
+import textwrap
 import weakref
 
 import pytest
@@ -69,6 +71,29 @@ def test_raw_copy():
  assert ref() is None
 
 
+def test_raw_copy_doesnt_leak():
+ """See https://github.com/jcrist/msgspec/pull/709"""
+ script = textwrap.dedent(
+ """
+ import msgspec
+ import tracemalloc
+
+ tracemalloc.start()
+
+ raw = msgspec.Raw(bytearray(1000))
+ for _ in range(10000):
+ raw.copy()
+
+ _, peak = tracemalloc.get_traced_memory()
+ print(peak)
+ """
+ )
+
+ output = subprocess.check_output([sys.executable, "-c", script])
+ peak = int(output.decode().strip())
+ assert peak < 10_000 # should really be ~2000
+
+
 def test_raw_pickle_bytes():
  orig_buffer = b"test"
  r = msgspec.Raw(orig_buffer)