Simplify beam writing mechanism

15 files changed, 116 insertions, 203 deletions

diff --git a/.gitignore b/.gitignore
index d4d844e04..9f5a6a247 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,7 +4,6 @@
 /ebin
 /lib/*/ebin/*
 /lib/*/tmp
-/lib/*/test/tmp
 /lib/elixir/src/elixir.app.src
 /lib/elixir/src/*_lexer.erl
 /lib/elixir/src/*_parser.erl
diff --git a/lib/elixir/lib/module.ex b/lib/elixir/lib/module.ex
index 546cc9595..b0405cb09 100644
--- a/lib/elixir/lib/module.ex
+++ b/lib/elixir/lib/module.ex
@@ -537,7 +537,7 @@ defmodule Module do
   end
 
   defp simplify_signature({var, _, atom}, _i) when is_atom(atom) do
-    case atom_to_binary(var) do
+    case Atom.to_string(var) do
       "_" <> rest -> {String.to_atom(rest), [], Elixir}
       _           -> {var, [], nil}
     end
diff --git a/lib/elixir/test/common_test_helpers.exs b/lib/elixir/test/common_test_helpers.exs
deleted file mode 100644
index 1218b301b..000000000
--- a/lib/elixir/test/common_test_helpers.exs
+++ /dev/null
@@ -1,38 +0,0 @@
-defmodule CodeHelpers do
-  defp fixture_dir() do
-    Path.expand("elixir/fixtures/docs", __DIR__)
-  end
-
-  def enter_fixture_dir() do
-    Path.wildcard(fixture_dir <> "/*.beam")
-    |> Enum.map(&File.rm/1)
-    Code.prepend_path(fixture_dir)
-    :ok
-  end
-
-  def leave_fixture_dir() do
-    :code.get_path()
-    |> List.delete(fixture_dir)
-    |> :code.set_path()
-    :ok
-  end
-
-  defmacro defbeam(kind \\ :module, name, do_body) do
-    mod = case kind do
-      :module ->
-        quote do
-          name = unquote(name); defmodule(name, unquote(do_body))
-        end
-
-      :protocol ->
-        quote do
-          name = unquote(name); defprotocol(name, unquote(do_body))
-        end
-    end
-    quote do
-      {:module, _, bin, _} = unquote(mod)
-      beam_path = Path.join(unquote(fixture_dir), atom_to_binary(name) <> ".beam")
-      File.write!(beam_path, bin)
-    end
-  end
-end
diff --git a/lib/elixir/test/elixir/fixtures/docs/README b/lib/elixir/test/elixir/fixtures/docs/README
deleted file mode 100644
index 68bb90170..000000000
--- a/lib/elixir/test/elixir/fixtures/docs/README
+++ /dev/null
@@ -1,2 +0,0 @@
-This directory is reserved for storing temporary .beam files. It is used by
-tests that need to access module docs.
diff --git a/lib/elixir/test/elixir/kernel/docs_test.exs b/lib/elixir/test/elixir/kernel/docs_test.exs
index 3747bf8ab..1b0d55a49 100644
--- a/lib/elixir/test/elixir/kernel/docs_test.exs
+++ b/lib/elixir/test/elixir/kernel/docs_test.exs
@@ -3,26 +3,14 @@ Code.require_file "../test_helper.exs", __DIR__
 defmodule Kernel.DocsTest do
   use ExUnit.Case
 
-  setup_all do
-    CodeHelpers.enter_fixture_dir()
-  end
-
-  teardown_all do
-    CodeHelpers.leave_fixture_dir()
-  end
-
   test "compiled with docs" do
-    expected = [
-      {{:fun, 2}, 60, :def, [{:x, [], nil}, {:y, [], nil}], "This is fun!\n"},
-      {{:nofun, 0}, 67, :def, [], nil},
-      {{:sneaky, 1}, 65, :def, [{:bool1, [], Elixir}], false},
-    ]
-
     deftestmodule(SampleDocs)
-
     docs = Code.get_docs(SampleDocs, :all)
-    assert docs[:docs] == expected
-    assert docs[:moduledoc] == {54, "Hello, I am a module"}
+
+    assert [{{:fun, 2}, _, :def, [{:x, [], nil}, {:y, [], nil}], "This is fun!\n"},
+            {{:nofun, 0}, _, :def, [], nil},
+            {{:sneaky, 1}, _, :def, [{:bool1, [], Elixir}], false}] = docs[:docs]
+    assert {_, "Hello, I am a module"} = docs[:moduledoc]
   end
 
   test "compiled without docs" do
@@ -36,7 +24,7 @@ defmodule Kernel.DocsTest do
     Code.compiler_options(docs: true)
   end
 
-  test "compiled in memory" do
+  test "compiled in memory does not have accessible docs" do
     defmodule NoDocs do
       @moduledoc "moduledoc"
 
@@ -49,9 +37,9 @@ defmodule Kernel.DocsTest do
   end
 
   defp deftestmodule(name) do
-    import CodeHelpers, only: [defbeam: 2]
+    import PathHelpers
 
-    defbeam name do
+    write_beam(defmodule name do
       @moduledoc "Hello, I am a module"
 
       @doc """
@@ -67,6 +55,6 @@ defmodule Kernel.DocsTest do
       def nofun() do
         'not fun at all'
       end
-    end
+    end)
   end
 end
diff --git a/lib/elixir/test/elixir/protocol_test.exs b/lib/elixir/test/elixir/protocol_test.exs
index a8d8bb8d5..09912c954 100644
--- a/lib/elixir/test/elixir/protocol_test.exs
+++ b/lib/elixir/test/elixir/protocol_test.exs
@@ -3,14 +3,6 @@ Code.require_file "test_helper.exs", __DIR__
 defmodule ProtocolTest do
   use ExUnit.Case, async: true
 
-  setup_all do
-    CodeHelpers.enter_fixture_dir()
-  end
-
-  teardown_all do
-    CodeHelpers.leave_fixture_dir()
-  end
-
   defprotocol Sample do
     @type t :: any
     @doc "Ok"
@@ -97,14 +89,14 @@ defmodule ProtocolTest do
   end
 
   test "protocol documentation" do
-    import CodeHelpers, only: [defbeam: 3]
+    import PathHelpers
 
-    defbeam :protocol, SampleDocsProto do
+    write_beam(defprotocol SampleDocsProto do
       @type t :: any
       @doc "Ok"
       @spec ok(t) :: boolean
       def ok(thing)
-    end
+    end)
 
     docs = Code.get_docs(SampleDocsProto, :docs)
     assert {{:ok, 1}, _, :def, [{:thing, _, nil}], "Ok"} =
@@ -119,10 +111,10 @@ defmodule ProtocolTest do
 
   test "protocol defines callbacks" do
     assert get_callbacks(Sample, :ok, 1) ==
-      [{:type, 17, :fun, [{:type, 17, :product, [{:type, 17, :t, []}]}, {:type, 17, :boolean, []}]}]
+      [{:type, 9, :fun, [{:type, 9, :product, [{:type, 9, :t, []}]}, {:type, 9, :boolean, []}]}]
 
     assert get_callbacks(WithAny, :ok, 1) ==
-      [{:type, 24, :fun, [{:type, 24, :product, [{:type, 24, :t, []}]}, {:type, 24, :term, []}]}]
+      [{:type, 16, :fun, [{:type, 16, :product, [{:type, 16, :t, []}]}, {:type, 16, :term, []}]}]
   end
 
   test "protocol defines attributes" do
diff --git a/lib/elixir/test/elixir/test_helper.exs b/lib/elixir/test/elixir/test_helper.exs
index ffc01a98d..6edf43dd1 100644
--- a/lib/elixir/test/elixir/test_helper.exs
+++ b/lib/elixir/test/elixir/test_helper.exs
@@ -1,7 +1,11 @@
-Code.require_file "../common_test_helpers.exs", __DIR__
-
 ExUnit.start [trace: "--trace" in System.argv]
 
+# Beam files compiled on demand
+path = Path.expand("../../tmp/beams", __DIR__)
+File.rm_rf!(path)
+File.mkdir_p!(path)
+Code.prepend_path(path)
+
 Code.compiler_options debug_info: true
 
 defmodule PathHelpers do
@@ -37,6 +41,13 @@ defmodule PathHelpers do
     executable_path("elixirc")
   end
 
+  def write_beam({:module, name, bin, _} = res) do
+    File.mkdir_p!(unquote(path))
+    beam_path = Path.join(unquote(path), Atom.to_string(name) <> ".beam")
+    File.write!(beam_path, bin)
+    res
+  end
+
   defp runcmd(executable,args) do
     :os.cmd :binary.bin_to_list("#{executable} #{IO.chardata_to_string(args)}#{redirect_std_err_on_win}")
   end
diff --git a/lib/ex_unit/test/ex_unit/doc_test_test.exs b/lib/ex_unit/test/ex_unit/doc_test_test.exs
index dced0fc48..64108f70d 100644
--- a/lib/ex_unit/test/ex_unit/doc_test_test.exs
+++ b/lib/ex_unit/test/ex_unit/doc_test_test.exs
@@ -1,12 +1,8 @@
 Code.require_file "../test_helper.exs", __DIR__
 
-# cleanup leftover .beam files before writing new modules
-CodeHelpers.enter_fixture_dir()
+import PathHelpers
 
-import CodeHelpers, only: [defbeam: 2]
-
-
-defbeam ExUnit.DocTestTest.GoodModule do
+defmodule ExUnit.DocTestTest.GoodModule do
   @doc """
   iex> test_fun
   1
@@ -51,9 +47,9 @@ defbeam ExUnit.DocTestTest.GoodModule do
   #HashDict<[c: 2, b: 1, a: 0]>
   """
   def inspect2_test, do: :ok
-end
+end |> write_beam
 
-defbeam ExUnit.DocTestTest.MultipleExceptions do
+defmodule ExUnit.DocTestTest.MultipleExceptions do
   @doc """
   iex> 1 + ""
   ** (ArithmeticError) bad argument in arithmetic expression
@@ -61,9 +57,9 @@ defbeam ExUnit.DocTestTest.MultipleExceptions do
   ** (ArithmeticError) bad argument in arithmetic expression
   """
   def two_exceptions, do: :ok
-end
+end |> write_beam
 
-defbeam ExUnit.DocTestTest.SomewhatGoodModuleWithOnly do
+defmodule ExUnit.DocTestTest.SomewhatGoodModuleWithOnly do
   @doc """
   iex> test_fun
   1
@@ -79,9 +75,9 @@ defbeam ExUnit.DocTestTest.SomewhatGoodModuleWithOnly do
   1
   """
   def test_fun1, do: 1
-end
+end |> write_beam
 
-defbeam ExUnit.DocTestTest.SomewhatGoodModuleWithExcept do
+defmodule ExUnit.DocTestTest.SomewhatGoodModuleWithExcept do
   @doc """
   iex> test_fun
   1
@@ -97,17 +93,17 @@ defbeam ExUnit.DocTestTest.SomewhatGoodModuleWithExcept do
   1
   """
   def test_fun1, do: 1
-end
+end |> write_beam
 
-defbeam ExUnit.DocTestTest.NoImport do
+defmodule ExUnit.DocTestTest.NoImport do
   @doc """
   iex> ExUnit.DocTestTest.NoImport.min(1, 2)
   2
   """
   def min(a, b), do: max(a, b)
-end
+end |> write_beam
 
-defbeam ExUnit.DocTestTest.Invalid do
+defmodule ExUnit.DocTestTest.Invalid do
   @moduledoc """
 
       iex> 1 + * 1
@@ -129,9 +125,9 @@ defbeam ExUnit.DocTestTest.Invalid do
       ** (RuntimeError) hello
 
   """
-end
+end |> write_beam
 
-defbeam ExUnit.DocTestTest.IndentationHeredocs do
+defmodule ExUnit.DocTestTest.IndentationHeredocs do
   @doc ~S'''
   Receives a test and formats its failure.
 
@@ -145,9 +141,9 @@ defbeam ExUnit.DocTestTest.IndentationHeredocs do
 
   '''
   def heredocs, do: :ok
-end
+end |> write_beam
 
-defbeam ExUnit.DocTestTest.IndentationMismatchedPrompt do
+defmodule ExUnit.DocTestTest.IndentationMismatchedPrompt do
   @doc ~S'''
     iex> foo = 1
      iex> bar = 2
@@ -155,42 +151,38 @@ defbeam ExUnit.DocTestTest.IndentationMismatchedPrompt do
     3
   '''
   def mismatched, do: :ok
-end
+end |> write_beam
 
-defbeam ExUnit.DocTestTest.IndentationTooMuch do
+defmodule ExUnit.DocTestTest.IndentationTooMuch do
   @doc ~S'''
     iex> 1 + 2
       3
   '''
   def too_much, do: :ok
-end
+end |> write_beam
 
-defbeam ExUnit.DocTestTest.IndentationNotEnough do
+defmodule ExUnit.DocTestTest.IndentationNotEnough do
   @doc ~S'''
       iex> 1 + 2
     3
   '''
   def not_enough, do: :ok
-end
+end |> write_beam
 
-defbeam ExUnit.DocTestTest.Incomplete do
+defmodule ExUnit.DocTestTest.Incomplete do
   @doc ~S'''
       iex> 1 + 2
 
   '''
   def not_enough, do: :ok
-end
+end |> write_beam
 
 defmodule ExUnit.DocTestTest do
   use ExUnit.Case
 
-  teardown_all do
-    CodeHelpers.leave_fixture_dir()
-  end
-
   # This is intentional. The doctests in DocTest's docs
   # fail for demonstration purposes.
-  #doctest ExUnit.DocTest
+  # doctest ExUnit.DocTest
 
   doctest ExUnit.DocTestTest.GoodModule, import: true
   doctest ExUnit.DocTestTest.SomewhatGoodModuleWithOnly, only: [test_fun: 0], import: true
@@ -211,58 +203,58 @@ defmodule ExUnit.DocTestTest do
 
     assert output =~ """
       1) test moduledoc at ExUnit.DocTestTest.Invalid (1) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:206
-         Doctest did not compile, got: (SyntaxError) test/ex_unit/doc_test_test.exs:110: syntax error before: '*'
+         test/ex_unit/doc_test_test.exs:198
+         Doctest did not compile, got: (SyntaxError) test/ex_unit/doc_test_test.exs:106: syntax error before: '*'
          code: 1 + * 1
          stacktrace:
-           test/ex_unit/doc_test_test.exs:110: ExUnit.DocTestTest.Invalid (module)
+           test/ex_unit/doc_test_test.exs:106: ExUnit.DocTestTest.Invalid (module)
     """
 
     assert output =~ """
       2) test moduledoc at ExUnit.DocTestTest.Invalid (2) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:206
+         test/ex_unit/doc_test_test.exs:198
          Doctest failed
          code: 1 + hd(List.flatten([1])) === 3
          lhs:  2
          stacktrace:
-           test/ex_unit/doc_test_test.exs:110: ExUnit.DocTestTest.Invalid (module)
+           test/ex_unit/doc_test_test.exs:106: ExUnit.DocTestTest.Invalid (module)
     """
 
     assert output =~ """
       3) test moduledoc at ExUnit.DocTestTest.Invalid (3) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:206
+         test/ex_unit/doc_test_test.exs:198
          Doctest failed
          code: inspect(:oops) === "#HashDict<[]>"
          lhs:  ":oops"
          stacktrace:
-           test/ex_unit/doc_test_test.exs:110: ExUnit.DocTestTest.Invalid (module)
+           test/ex_unit/doc_test_test.exs:106: ExUnit.DocTestTest.Invalid (module)
     """
 
     assert output =~ """
       4) test moduledoc at ExUnit.DocTestTest.Invalid (4) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:206
+         test/ex_unit/doc_test_test.exs:198
          Doctest failed: got UndefinedFunctionError with message undefined function: Hello.world/0
          code:  Hello.world
          stacktrace:
-           test/ex_unit/doc_test_test.exs:110: ExUnit.DocTestTest.Invalid (module)
+           test/ex_unit/doc_test_test.exs:106: ExUnit.DocTestTest.Invalid (module)
     """
 
     assert output =~ """
       5) test moduledoc at ExUnit.DocTestTest.Invalid (5) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:206
+         test/ex_unit/doc_test_test.exs:198
          Doctest failed: expected exception WhatIsThis with message "oops" but got RuntimeError with message "oops"
          code: raise "oops"
          stacktrace:
-           test/ex_unit/doc_test_test.exs:110: ExUnit.DocTestTest.Invalid (module)
+           test/ex_unit/doc_test_test.exs:106: ExUnit.DocTestTest.Invalid (module)
     """
 
     assert output =~ """
       6) test moduledoc at ExUnit.DocTestTest.Invalid (6) (ExUnit.DocTestTest.ActuallyCompiled)
-         test/ex_unit/doc_test_test.exs:206
+         test/ex_unit/doc_test_test.exs:198
          Doctest failed: expected exception RuntimeError with message "hello" but got RuntimeError with message "oops"
          code: raise "oops"
          stacktrace:
-           test/ex_unit/doc_test_test.exs:110: ExUnit.DocTestTest.Invalid (module)
+           test/ex_unit/doc_test_test.exs:106: ExUnit.DocTestTest.Invalid (module)
     """
   end
 
diff --git a/lib/ex_unit/test/test_helper.exs b/lib/ex_unit/test/test_helper.exs
index 06488430a..e7e72338e 100644
--- a/lib/ex_unit/test/test_helper.exs
+++ b/lib/ex_unit/test/test_helper.exs
@@ -1,3 +1,15 @@
-Code.require_file "../../elixir/test/common_test_helpers.exs", __DIR__
-
 ExUnit.start [trace: "--trace" in System.argv]
+
+# Beam files compiled on demand
+path = Path.expand("../tmp/beams", __DIR__)
+File.rm_rf!(path)
+File.mkdir_p!(path)
+Code.prepend_path(path)
+
+defmodule PathHelpers do
+  def write_beam({:module, name, bin, _} = res) do
+    beam_path = Path.join(unquote(path), Atom.to_string(name) <> ".beam")
+    File.write!(beam_path, bin)
+    res
+  end
+end
diff --git a/lib/iex/lib/iex/autocomplete.ex b/lib/iex/lib/iex/autocomplete.ex
index 618a96492..0e0296ad0 100644
--- a/lib/iex/lib/iex/autocomplete.ex
+++ b/lib/iex/lib/iex/autocomplete.ex
@@ -46,7 +46,7 @@ defmodule IEx.Autocomplete do
       {:ok, {atom, _, nil}} when is_atom(atom) ->
         expand_call Kernel, Atom.to_string(atom)
       {:ok, {:__aliases__, _, [root]}} ->
-        expand_elixir_modules [], atom_to_binary(root)
+        expand_elixir_modules [], Atom.to_string(root)
       {:ok, {:__aliases__, _, [h|_] = list}} when is_atom(h) ->
         hint = Atom.to_string(List.last(list))
         list = Enum.take(list, length(list) - 1)
diff --git a/lib/iex/test/iex/helpers_test.exs b/lib/iex/test/iex/helpers_test.exs
index 2f2c90a28..fe132ef1a 100644
--- a/lib/iex/test/iex/helpers_test.exs
+++ b/lib/iex/test/iex/helpers_test.exs
@@ -3,27 +3,6 @@ Code.require_file "../test_helper.exs", __DIR__
 defmodule IEx.HelpersTest do
   use IEx.Case
 
-  setup_all do
-    CodeHelpers.enter_fixture_dir()
-    import CodeHelpers, only: [defbeam: 2]
-
-    defbeam IExDocsSample do
-      @doc """
-      Test function 1
-      """
-      def test_fun_1, do: :ok
-
-      @doc """
-      Test function 2
-      """
-      def test_fun_2(arg \\ 99), do: arg
-    end
-  end
-
-  teardown_all do
-    CodeHelpers.leave_fixture_dir()
-  end
-
   import IEx.Helpers
 
   test "clear helper" do
@@ -47,18 +26,14 @@ defmodule IEx.HelpersTest do
   end
 
   test "h helper function" do
-    doc_1 = "* def test_fun_1()\n\nTest function 1\n\n"
-    doc_2 = "* def test_fun_2(arg \\\\ 99)\n\nTest function 2\n\n"
-
-    assert capture_io(fn -> h IExDocsSample.test_fun_1/0 end) == doc_1
-    assert capture_io(fn -> h IExDocsSample.test_fun_2/1 end) == doc_2
+    pwd_h = "* def pwd()\n\nPrints the current working directory.\n\n"
+    c_h   = "* def c(files, path \\\\ \".\")\n\nExpects a list of files to compile"
 
-    output = capture_io(fn -> h IExDocsSample.test_fun_1 end)
-    assert :binary.match(output, doc_1)
-    assert :binary.match(output, doc_2)
+    assert capture_io(fn -> h IEx.Helpers.pwd/0 end) =~ pwd_h
+    assert capture_io(fn -> h IEx.Helpers.c/2 end) =~ c_h
 
-    assert capture_io(fn -> h pwd end)
-           == "* def pwd()\n\nPrints the current working directory.\n\n\n"
+    assert capture_io(fn -> h Iex.Helpers.c/1 end) =~ c_h
+    assert capture_io(fn -> h pwd end) =~ pwd_h
   end
 
   test "h helper __info__" do
diff --git a/lib/iex/test/iex/interaction_test.exs b/lib/iex/test/iex/interaction_test.exs
index 695c25713..6d3de2054 100644
--- a/lib/iex/test/iex/interaction_test.exs
+++ b/lib/iex/test/iex/interaction_test.exs
@@ -3,22 +3,6 @@ Code.require_file "../test_helper.exs", __DIR__
 defmodule IEx.InteractionTest do
   use IEx.Case
 
-  setup_all do
-    CodeHelpers.enter_fixture_dir()
-    import CodeHelpers, only: [defbeam: 2]
-
-    defbeam IExModuledocSample do
-      @doc """
-      Hello, I have %{red}ANSI%{reset} escapes.
-      """
-      def ansi_escapes, do: :ok
-    end
-  end
-
-  teardown_all do
-    CodeHelpers.leave_fixture_dir()
-  end
-
   ## Basic interaction
 
   test "whole output" do
@@ -123,8 +107,8 @@ defmodule IEx.InteractionTest do
 
       # Test that ANSI escapes in the docs are left alone
       opts = [colors: [enabled: true]]
-      assert capture_iex("h IExModuledocSample.ansi_escapes", opts)
-             =~ ~r"Hello, I have %\{red}ANSI%\{reset} escapes"
+      assert capture_iex("h IO.ANSI.escape_fragment", opts)
+             =~ ~r"%\{red\}"
 
       # Test that ANSI escapes in iex output are left alone
       opts = [colors: [enabled: true, eval_result: "red", eval_info: "red"]]
diff --git a/lib/iex/test/test_helper.exs b/lib/iex/test/test_helper.exs
index 755d0b718..38e6f57a2 100644
--- a/lib/iex/test/test_helper.exs
+++ b/lib/iex/test/test_helper.exs
@@ -1,5 +1,3 @@
-Code.require_file "../../elixir/test/common_test_helpers.exs", __DIR__
-
 Application.start(:iex)
 Application.put_env(:iex, :colors, [enabled: false])
 ExUnit.start [trace: "--trace" in System.argv]
diff --git a/lib/mix/test/mix/task_test.exs b/lib/mix/test/mix/task_test.exs
index 976410efc..48f08fe85 100644
--- a/lib/mix/test/mix/task_test.exs
+++ b/lib/mix/test/mix/task_test.exs
@@ -1,28 +1,37 @@
 Code.require_file "../test_helper.exs", __DIR__
 
-defmodule Mix.TaskTest do
-  use MixTest.Case
-
-  setup_all do
-    CodeHelpers.enter_fixture_dir()
-    import CodeHelpers, only: [defbeam: 2]
+path = MixTest.Case.tmp_path("beams")
+File.rm_rf!(path)
+File.mkdir_p!(path)
+
+write_beam = fn {:module, name, bin, _} ->
+  path
+  |> Path.join(Atom.to_string(name) <> ".beam")
+  |> File.write!(bin)
+end
 
-    defbeam Mix.Tasks.Hello do
-      use Mix.Task
-      @shortdoc "This is short documentation, see"
+defmodule Mix.Tasks.Hello do
+  use Mix.Task
+  @shortdoc "This is short documentation, see"
 
-      @moduledoc """
-      A test task.
-      """
+  @moduledoc """
+  A test task.
+  """
 
-      def run(_) do
-        "Hello, World!"
-      end
-    end
+  def run(_) do
+    "Hello, World!"
   end
+end |> write_beam.()
+
+defmodule Mix.Tasks.Invalid do
+end |> write_beam.()
+
+defmodule Mix.TaskTest do
+  use MixTest.Case
 
-  teardown_all do
-    CodeHelpers.leave_fixture_dir()
+  setup do
+    Code.prepend_path unquote(path)
+    :ok
   end
 
   test :run do
diff --git a/lib/mix/test/test_helper.exs b/lib/mix/test/test_helper.exs
index a5f147817..10a36a9f1 100644
--- a/lib/mix/test/test_helper.exs
+++ b/lib/mix/test/test_helper.exs
@@ -1,5 +1,3 @@
-Code.require_file "../../elixir/test/common_test_helpers.exs", __DIR__
-
 Mix.start()
 Mix.shell(Mix.Shell.Process)
 
@@ -107,15 +105,10 @@ defmodule MixTest.Case do
   end
 end
 
-## Some tasks fixtures
-
-defmodule Mix.Tasks.Invalid do
-end
-
 ## Copy fixtures to tmp
 
 source = MixTest.Case.fixture_path("rebar_dep")
-dest = Path.join(MixTest.Case.tmp_path, "rebar_dep")
+dest = MixTest.Case.tmp_path("rebar_dep")
 File.mkdir_p!(dest)
 File.cp_r!(source, dest)