Ensure proper error message on mix test when there is no test directory

Author: josevalim

lib/mix/lib/mix/compilers/test.ex

@@ -32,6 +32,8 @@ defmodule Mix.Compilers.Test do
         {matched_test_files, nil, []}
       end
 
+    Application.ensure_all_started(:ex_unit)
+
     cond do
       test_files == [] ->
         # Make sure we run the after_suite callbacks but with no feedback

lib/mix/test/mix/tasks/test_test.exs

@@ -411,9 +411,10 @@ defmodule Mix.Tasks.TestTest do
     test "logs test absence for a project with no test paths" do
       in_fixture("test_stale", fn ->
         File.rm_rf!("test")
+        assert_run_output("There are no tests to run")
+
         File.mkdir_p!("test")
         File.write!("test/test_helper.exs", "ExUnit.start()")
-
         assert_run_output("There are no tests to run")
       end)
     end