Force koan order using macros and attributes

lib/koans.ex

@@ -3,7 +3,9 @@ defmodule Koans do
 
   defmacro koan(name, body) do
     compiled_name = :"#{prefix}#{name}"
+
     quote do
+      @koans unquote(compiled_name)
       def unquote(compiled_name)() do
         try do
           unquote(body)
@@ -17,9 +19,12 @@ defmodule Koans do
 
   defmacro __using__(opts) do
     quote do
+      Module.register_attribute(__MODULE__, :koans, accumulate: true)
       require ExUnit.Assertions
       import Koans
       import BlankAssertions
+
+      @before_compile KoansBuilder
     end
   end
 
@@ -27,3 +32,14 @@ defmodule Koans do
     @prefix
   end
 end
+
+defmodule KoansBuilder do
+  defmacro __before_compile__(env) do
+    koans = Module.get_attribute(env.module, :koans) |> Enum.reverse
+    quote do
+      def all_koans do
+        unquote(koans)
+      end
+    end
+  end
+end

lib/runner.ex

@@ -51,8 +51,7 @@ defmodule Runner do
   end
 
   defp extract_koans_from(module) do
-    module.__info__(:functions)
-    |> Enum.map(fn({name, _arity}) -> name end)
+    module.all_koans
     |> Enum.filter(&koan?/1)
   end