Implement returning Box from Rust to C++
diff --git a/tests/ffi/tests.cc b/tests/ffi/tests.cc
index 7b77c07..3d30ebe 100644
--- a/tests/ffi/tests.cc
+++ b/tests/ffi/tests.cc
@@ -102,6 +102,7 @@
 
   ASSERT(r_return_primitive() == 2020);
   ASSERT(r_return_shared().z == 2020);
+  ASSERT(cxx_test_suite_r_is_correct(&*r_return_box()));
   ASSERT(r_return_ref(Shared{2020}) == 2020);
   ASSERT(std::string(r_return_str(Shared{2020})) == "2020");
   ASSERT(std::string(r_return_rust_string()) == "2020");