Fix. Mock not working for grandchildren and beyond (#746)

fix: Mock not working for grandchilden and beyond

Author: carrascoacd

lib/tesla/mock.ex

@@ -231,7 +231,13 @@ defmodule Tesla.Mock do
   defp pdict_get do
     pid_holder =
       Enum.find(Process.get(:"$ancestors", []), self(), fn ancestor ->
-        !is_nil(Process.get(ancestor, __MODULE__))
+        is_holder? =
+          ancestor
+          |> Process.info()
+          |> Keyword.get(:dictionary)
+          |> Keyword.get(__MODULE__)
+
+        !is_nil(is_holder?)
       end)
       |> case do
         nil -> raise "Unknown pid_holder in mock"

test/tesla/mock_test.exs

@@ -85,15 +85,31 @@ defmodule Tesla.MockTest do
       assert env.body == %{"id" => 42}
     end
 
-    test "mock a request inside a spawned process" do
-      task =
+    test "mock a request inside a child process" do
+      child_task =
         Task.async(fn ->
           assert {:ok, %Tesla.Env{} = env} = Client.get("/json")
           assert env.status == 200
           assert env.body == %{"json" => 123}
         end)
 
-      Task.await(task)
+      Task.await(child_task)
+    end
+
+    test "mock a request inside a grandchild process" do
+      grandchild_task =
+        Task.async(fn ->
+          child_task =
+            Task.async(fn ->
+              assert {:ok, %Tesla.Env{} = env} = Client.get("/json")
+              assert env.status == 200
+              assert env.body == %{"json" => 123}
+            end)
+
+          Task.await(child_task)
+        end)
+
+      Task.await(grandchild_task)
     end
   end