Add test for resource binary

Author: jonatanklosko

test/c_src/finest.cpp

@@ -20,8 +20,9 @@ auto y = fine::Atom("y");
 
 struct TestResource {
   ErlNifPid pid;
+  std::string binary;
 
-  TestResource(ErlNifPid pid) : pid(pid) {}
+  TestResource(ErlNifPid pid) : pid(pid), binary("hello world") {}
 
   void destructor(ErlNifEnv *env) {
     auto msg_env = enif_alloc_env();
@@ -186,6 +187,13 @@ ErlNifPid resource_get(ErlNifEnv *, fine::ResourcePtr<TestResource> resource) {
 }
 FINE_NIF(resource_get, 0);
 
+fine::Term resource_binary(ErlNifEnv *env,
+                           fine::ResourcePtr<TestResource> resource) {
+  return fine::make_resource_binary(env, resource, resource->binary.data(),
+                                    resource->binary.size());
+}
+FINE_NIF(resource_binary, 0);
+
 fine::Term make_new_binary(ErlNifEnv *env) {
   const char *buffer = "hello world";
   size_t size = 11;

test/lib/finest/nif.ex

@@ -40,6 +40,7 @@ defmodule Finest.NIF do
 
   def resource_create(_pid), do: err!()
   def resource_get(_resource), do: err!()
+  def resource_binary(_resource), do: err!()
 
   def make_new_binary(), do: err!()
 

test/test/finest_test.exs

@@ -232,6 +232,26 @@ defmodule FinestTest do
       assert_receive :destructor_with_env
       assert_receive :destructor_default
     end
+
+    test "resource binary keeps reference to the resource" do
+      _ =
+        (fn ->
+           binary = NIF.resource_binary(NIF.resource_create(self()))
+           :erlang.garbage_collect(self())
+
+           # We have reference to the binary, so the resource should
+           # stay alive.
+           refute_receive :destructor_default, 10
+
+           byte_size(binary)
+         end).()
+
+      # We no longer have reference to the binary, so GC should destroy
+      # the resource.
+      :erlang.garbage_collect(self())
+
+      assert_receive :destructor_default
+    end
   end
 
   describe "make_new_binary" do