Add tests for memory leaks

dev-requirements.txt

@@ -8,3 +8,4 @@ trustme
 requests
 flaky
 httpx
+pytest-memray; python_version<"3.12" and sys_platform!="win32" and implementation_name=="cpython"

noxfile.py

@@ -52,11 +52,17 @@ def test(session):
 
     session.install("-rdev-requirements.txt", ".")
     session.run("pip", "freeze")
+    memray_supported = not session.run("python", "-c", '"import pytest_memray"')
+    memray_posargs: tuple[str, ...] = (
+        ("--memray", "--hide-memray-summary") if memray_supported else ()
+    )
+
     session.run(
         "pytest",
         "-v",
         "-s",
         "-rs",
+        *memray_posargs,
         "--no-flaky-report",
         "--max-runs=3",
         *(session.posargs or ("tests/",)),

pyproject.toml

@@ -34,3 +34,6 @@ asyncio_mode = "strict"
 filterwarnings = [
   "error",
 ]
+markers = [
+  "limit_memory"
+]

tests/test_memory.py

@@ -0,0 +1,31 @@
+import asyncio
+import ssl
+
+import pytest
+import urllib3
+
+import truststore
+
+from .conftest import Server
+
+try:
+    import pytest_memray  # noqa: F401
+
+    memray_installed = True
+except ImportError:
+    memray_installed = False
+
+
+@pytest.mark.skipif(not memray_installed, reason="Memray isn't installed")
+@pytest.mark.limit_memory("1MB")
+@pytest.mark.asyncio
+async def test_memory_limit(server: Server) -> None:
+    def run_requests():
+        ctx = truststore.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+        for _ in range(10000):
+            with urllib3.PoolManager(ssl_context=ctx) as http:
+                http.request("GET", server.base_url)
+                http.clear()  # Close connections so we get new ones.
+
+    thread = asyncio.to_thread(run_requests)
+    await thread