Make ExUnit tmp_dir absolute (#10826)

Author: wojtekmach

lib/ex_unit/lib/ex_unit/runner.ex

@@ -394,7 +394,7 @@ defmodule ExUnit.Runner do
   defp create_tmp_dir!(test, extra_path, context) do
     module = escape_path(inspect(test.module))
     name = escape_path(to_string(test.name))
-    path = Path.join(["tmp", module, name, extra_path])
+    path = ["tmp", module, name, extra_path] |> Path.join() |> Path.expand()
     File.rm_rf!(path)
     File.mkdir_p!(path)
     Map.put(context, :tmp_dir, path)

lib/ex_unit/test/ex_unit/case_test.exs

@@ -156,17 +156,17 @@ defmodule ExUnit.CaseTest.TmpDir do
   @moduletag :tmp_dir
 
   test "default path", context do
-    assert context.tmp_dir == "tmp/ExUnit.CaseTest.TmpDir/test-default-path"
+    assert context.tmp_dir == Path.expand("tmp/ExUnit.CaseTest.TmpDir/test-default-path")
     assert File.ls!(context.tmp_dir) == []
   end
 
   test "escapes foo?/0", context do
-    assert context.tmp_dir == "tmp/ExUnit.CaseTest.TmpDir/test-escapes-foo--0"
+    assert context.tmp_dir == Path.expand("tmp/ExUnit.CaseTest.TmpDir/test-escapes-foo--0")
   end
 
   @tag tmp_dir: "foo/bar"
   test "custom path", context do
-    assert context.tmp_dir == "tmp/ExUnit.CaseTest.TmpDir/test-custom-path/foo/bar"
+    assert context.tmp_dir == Path.expand("tmp/ExUnit.CaseTest.TmpDir/test-custom-path/foo/bar")
   end
 
   @tag tmp_dir: false

lib/mix/test/mix_test.exs

@@ -75,7 +75,6 @@ defmodule MixTest do
 
       Mix.State.put(:install_called?, false)
 
-      tmp_dir = Path.expand(tmp_dir)
       File.mkdir_p!("#{tmp_dir}/install_test/lib")
 
       File.write!("#{tmp_dir}/install_test/mix.exs", """