Extract pure executor of koans

lib/execute.ex

@@ -0,0 +1,48 @@
+defmodule Execute do
+  def run_module(module) do
+    run_until_failure(module, &run_koan/2)
+  end
+
+  def run_until_failure(module, callback) do
+    Enum.reduce_while(module.all_koans, :passed, fn(it, _acc) ->
+      result = callback.(module, it)
+      if result == :passed do
+        {:cont, :passed}
+      else
+        {:halt, result}
+      end
+    end)
+  end
+
+  def run_koan(module, name, args \\ []) do
+    parent = self()
+    spawn fn -> exec(module, name, args, parent) end
+    receive do
+      :ok   -> :passed
+      error -> {:failed, error, module, name}
+    end
+  end
+
+  def exec(module, name, args, parent) do
+    result = apply(module, name, args)
+    send parent, expand(result)
+    Process.exit(self(), :kill)
+  end
+
+  def expand(:ok), do: :ok
+  def expand(error) do
+    {file, line} = System.stacktrace
+      |> Enum.drop_while(&in_ex_unit?/1)
+      |> List.first
+      |> extract_file_and_line
+
+      %{error: error, file: file, line: line}
+  end
+
+  defp in_ex_unit?({ExUnit.Assertions, _, _, _}), do: true
+  defp in_ex_unit?(_), do: false
+
+  defp extract_file_and_line({_, _, _, [file: file, line: line]}) do
+   {file, line}
+  end
+end

lib/runner.ex

@@ -34,50 +34,10 @@ defmodule Runner do
 
   def run_module(module) do
     Display.considering(module)
-
-    koans = module.all_koans
-    passed = Enum.take_while(koans, fn(name) ->
-      case run_koan(module, name) do
-        :passed -> true
+    case Execute.run_module(module) do
         {:failed, error, module, name} -> Display.show_failure(error, module, name)
-                                          false
-      end
-    end)
-
-    if Enum.count(koans) == Enum.count(passed) do
-      :passed
-    else
-      :failed
+                                          :failed
+        _ -> :passed
     end
   end
-
-  def run_koan(module, name, args \\ []) do
-    parent = self()
-    spawn fn -> exec(module, name, args, parent) end
-    receive do
-      :ok   -> :passed
-      error -> {:failed, error, module, name}
-    end
-  end
-
-  def exec(module, name, args, parent) do
-    result = apply(module, name, args)
-    send parent, expand(result)
-    Process.exit(self(), :kill)
-  end
-
-  def expand(:ok), do: :ok
-  def expand(error) do
-    {file, line} = System.stacktrace
-      |> Enum.drop_while(&in_ex_unit?/1)
-      |> List.first
-      |> extract_file_and_line
-
-      %{error: error, file: file, line: line}
-  end
-
-  defp in_ex_unit?({ExUnit.Assertions, _, _, _}), do: true
-  defp in_ex_unit?(_), do: false
-
-  defp extract_file_and_line({_, _, _, [file: file, line: line]}), do: {file, line}
 end

test/executor_test.exs

@@ -0,0 +1,13 @@
+defmodule RunnerTest do
+  use ExUnit.Case
+
+  test "passes a koan" do
+    assert :passed == Execute.run_module(PassingKoan)
+  end
+
+  test "stops at the first failing koan" do
+    {:failed, %{error: _, file: file, line: line}, SampleKoan, _name} = Execute.run_module(SampleKoan)
+    assert file == 'test/support/sample_koan.ex'
+    assert line == 5
+  end
+end

test/koans_harness_test.exs

@@ -232,6 +232,6 @@ defmodule KoansHarnessTest do
   end
 
   def run_all(pairs, module) do
-    Enum.map(pairs, fn ({koan, answer}) -> Runner.run_koan(module, koan, [answer]) end)
+    Enum.map(pairs, fn ({koan, answer}) -> Execute.run_koan(module, koan, [answer]) end)
   end
 end

test/support/passing_koan.ex

@@ -0,0 +1,7 @@
+defmodule PassingKoan do
+  use Koans
+
+  koan "hi there" do
+    assert 1 == 1
+  end
+end