Adding test_open_spiel_pattern. It builds and run with py::class_ or py::classh.

tests/test_open_spiel_pattern.cpp

+#include "pybind11_tests.h"
+
+#include <pybind11/functional.h>
+#include <pybind11/smart_holder.h>
+
+#include <functional>
+
+namespace pybind11_tests {
+namespace open_spiel_pattern {
+
+class Foo {
+public:
+    int num;
+    Foo(int i) : num{i} {}
+    int bar(int i) { return num + i; }
+};
+
+using FooFactory = std::function<Foo()>;
+
+int MakeAndUseFoo(FooFactory f) {
+    auto foo = f();
+    return foo.bar(456);
+}
+
+} // namespace open_spiel_pattern
+} // namespace pybind11_tests
+
+// To use py::smart_holder, uncomment the next line and change py::class_ below to py::classh.
+// PYBIND11_SMART_HOLDER_TYPE_CASTERS(pybind11_tests::open_spiel_pattern::Foo)
+
+TEST_SUBMODULE(open_spiel_pattern, m) {
+    using namespace pybind11_tests::open_spiel_pattern;
+
+    py::class_<Foo>(m, "Foo").def(py::init<int>()).def("bar", &Foo::bar);
+
+    m.def("make_and_use_foo", MakeAndUseFoo);
+}

tests/test_open_spiel_pattern.py

+# -*- coding: utf-8 -*-
+import pytest
+
+from pybind11_tests import open_spiel_pattern as m
+
+def test_make_and_use_foo():
+    res = m.make_and_use_foo(lambda : m.Foo(123))
+    assert res == 579