--- /dev/null
+++ xnu/xnu-12377.1.9/tests/intrusive_shared_ptr_src/assign.nullptr.cpp
@@ -0,0 +1,46 @@
+//
+// Tests for
+//  intrusive_shared_ptr& operator=(std::nullptr_t);
+//
+
+#include <libkern/c++/intrusive_shared_ptr.h>
+#include <darwintest.h>
+#include "test_policy.h"
+
+struct T {
+	int i;
+};
+
+template <typename T>
+static void
+tests()
+{
+	T obj{3};
+
+	// Assign nullptr to non-null
+	{
+		tracked_shared_ptr<T> ptr(&obj, libkern::retain);
+		tracking_policy::reset();
+		tracked_shared_ptr<T>& ref = (ptr = nullptr);
+		CHECK(tracking_policy::releases == 1);
+		CHECK(tracking_policy::retains == 0);
+		CHECK(&ref == &ptr);
+		CHECK(ptr.get() == nullptr);
+	}
+
+	// Assign nullptr to null
+	{
+		tracked_shared_ptr<T> ptr = nullptr;
+		tracking_policy::reset();
+		tracked_shared_ptr<T>& ref = (ptr = nullptr);
+		CHECK(tracking_policy::releases == 0);
+		CHECK(tracking_policy::retains == 0);
+		CHECK(&ref == &ptr);
+		CHECK(ptr.get() == nullptr);
+	}
+}
+
+T_DECL(assign_nullptr, "intrusive_shared_ptr.assign.nullptr", T_META_TAG_VM_PREFERRED) {
+	tests<T>();
+	tests<T const>();
+}