Verify duplicate dry-run results in tests

Author: Nezteb

lib/ex_unit/mix.exs

@@ -39,7 +39,8 @@ defmodule ExUnit.MixProject do
         timeout: 60000,
         trace: false,
         after_suite: [],
-        repeat_until_failure: 0
+        repeat_until_failure: 0,
+        dry_run: false
       ]
     ]
   end

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

@@ -39,11 +39,12 @@ defmodule Mix.Compilers.Test do
   end
 
   defp require_and_run(matched_test_files, test_paths, opts) do
-    stale = opts[:stale]
+    dry_run = Keyword.get(opts, :dry_run, false)
+    stale = Keyword.get(opts, :stale, false)
     max_requires = opts[:max_requires]
 
     {test_files, stale_manifest_pid, parallel_require_callbacks} =
-      if stale do
+      if stale and not dry_run do
         set_up_stale(matched_test_files, test_paths, opts)
       else
         {matched_test_files, nil, []}

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

@@ -741,34 +741,37 @@ defmodule Mix.Tasks.TestTest do
         """)
 
         output = mix(["test", "--dry-run", "--stale"])
-
         assert output =~ "Tests that would be executed:"
         assert output =~ "test/a_test_stale.exs:4"
         assert output =~ "test/b_test_stale.exs:4"
         assert output =~ "test/dry_run_one_test_stale.exs:4"
         refute output =~ "test/dry_run_two_test_stale.exs:5"
         assert output =~ "1 test, 0 failures, 1 skipped"
 
-        # Tests are still marked as stale
+        # Tests should still be marked as stale
         output = mix(["test", "--dry-run", "--stale"])
         assert output =~ "1 test, 0 failures, 1 skipped"
       end)
     end
 
     test "works with --failed" do
       in_fixture("test_failed", fn ->
-        _initial_run = mix(["test"])
-        output = mix(["test", "--dry-run", "--failed"])
+        output = mix(["test"])
+        assert output =~ "4 tests, 2 failures"
 
+        output = mix(["test", "--dry-run", "--failed"])
         assert output =~ "Tests that would be executed:"
         assert output =~ "test/only_failing_test_failed.exs:4"
         assert output =~ "test/passing_and_failing_test_failed.exs:5"
         assert output =~ "0 tests, 0 failures"
 
-        # Tests are still marked as failed
-        output = mix(["test", "--dry-run", "failed"])
+        # Force the tests to pass, verify dry-run doesn't actually run them
+        System.put_env("PASS_FAILING_TESTS", "true")
+        output = mix(["test", "--dry-run", "--failed"])
         assert output =~ "0 tests, 0 failures"
       end)
+    after
+      System.delete_env("PASS_FAILING_TESTS")
     end
   end