ci: fix clang warnings
diff --git a/tests/test_call_policies.cpp b/tests/test_call_policies.cpp
index fd24557..26c83f8 100644
--- a/tests/test_call_policies.cpp
+++ b/tests/test_call_policies.cpp
@@ -46,6 +46,7 @@
     class Parent {
     public:
         Parent() { py::print("Allocating parent."); }
+        Parent(const Parent& parent) = default;
         ~Parent() { py::print("Releasing parent."); }
         void addChild(Child *) { }
         Child *returnChild() { return new Child(); }