Tag async tests as such

Author: José Valim

lib/ex_unit/lib/ex_unit/case.ex

@@ -162,15 +162,17 @@ defmodule ExUnit.Case do
 
     quote do
       unless Module.get_attribute(__MODULE__, :ex_unit_tests) do
+        Enum.each [:ex_unit_tests, :tag, :moduletag],
+          &Module.register_attribute(__MODULE__, &1, accumulate: true)
+
         if unquote(async) do
+          @moduletag async: true
           ExUnit.Server.add_async_case(__MODULE__)
         else
+          @moduletag async: false
           ExUnit.Server.add_sync_case(__MODULE__)
         end
 
-        Enum.each [:ex_unit_tests, :tag, :moduletag],
-          &Module.register_attribute(__MODULE__, &1, accumulate: true)
-
         @before_compile ExUnit.Case
         use ExUnit.Callbacks
       end

lib/ex_unit/test/ex_unit/case_test.exs

@@ -19,6 +19,7 @@ defmodule ExUnit.CaseTest do
     assert context[:case] == __MODULE__
     assert context[:test] == __ENV__.function |> elem(0)
     assert context[:line] == line
+    assert context[:async] == true
     assert context[:hello] == true
     assert context[:world] == :good
   end