add unit test

Author: maxbachmann

tests/test_class.cpp

@@ -104,6 +104,10 @@ TEST_SUBMODULE(class_, m) {
         ~NoConstructorNew() { print_destroyed(this); }
     };
 
+    struct DynamicAttr {
+        DynamicAttr() = default;
+    };
+
     py::class_<NoConstructor>(m, "NoConstructor")
         .def_static("new_instance", &NoConstructor::new_instance, "Return an instance");
 
@@ -112,6 +116,9 @@ TEST_SUBMODULE(class_, m) {
         .def_static("__new__",
                     [](const py::object &) { return NoConstructorNew::new_instance(); });
 
+    py::class_<DynamicAttr>(m, "DynamicAttr", py::dynamic_attr())
+        .def(py::init<>());
+
     // test_pass_unique_ptr
     struct ToBeHeldByUniquePtr {};
     py::class_<ToBeHeldByUniquePtr, std::unique_ptr<ToBeHeldByUniquePtr>>(m, "ToBeHeldByUniquePtr")

tests/test_class.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import gc
 import sys
 from unittest import mock
 
@@ -45,6 +46,12 @@ def test_instance(msg):
     assert cstats.alive() == 0
 
 
+def test_get_referrers():
+    instance = m.DynamicAttr()
+    instance.a = "test"
+    assert instance in gc.get_referrers(instance.__dict__)
+
+
 def test_instance_new():
     instance = m.NoConstructorNew()  # .__new__(m.NoConstructor.__class__)