os: clean up tests

- Use testenv.Command instead of exec.Command to try to get more
  useful timeout behavior.

- Parallelize tests that appear not to require global state.
  (And add explanatory comments for a few that are not
  parallelizable for subtle reasons.)

- Consolidate some “Helper” tests with their parent tests.

- Use t.TempDir instead of os.MkdirTemp when appropriate.

- Factor out subtests for repeated test helpers.

For #36107.
Updates #22315.

Change-Id: Ic24b6957094dcd40908a59f48e44c8993729222b
Reviewed-on: https://go-review.googlesource.com/c/go/+/458015
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/os/path_windows_test.go b/src/os/path_windows_test.go
index e960bcb19c..2506b4f0d8 100644
--- a/src/os/path_windows_test.go
+++ b/src/os/path_windows_test.go
@@ -15,6 +15,8 @@ func TestFixLongPath(t *testing.T) {
 	if os.CanUseLongPaths {
 		return
 	}
+	t.Parallel()
+
 	// 248 is long enough to trigger the longer-than-248 checks in
 	// fixLongPath, but short enough not to make a path component
 	// longer than 255, which is illegal on Windows. (which
@@ -50,6 +52,8 @@ func TestFixLongPath(t *testing.T) {
 }
 
 func TestMkdirAllLongPath(t *testing.T) {
+	t.Parallel()
+
 	tmpDir := t.TempDir()
 	path := tmpDir
 	for i := 0; i < 100; i++ {
@@ -64,6 +68,7 @@ func TestMkdirAllLongPath(t *testing.T) {
 }
 
 func TestMkdirAllExtendedLength(t *testing.T) {
+	t.Parallel()
 	tmpDir := t.TempDir()
 
 	const prefix = `\\?\`
@@ -86,6 +91,8 @@ func TestMkdirAllExtendedLength(t *testing.T) {
 }
 
 func TestOpenRootSlash(t *testing.T) {
+	t.Parallel()
+
 	tests := []string{
 		`/`,
 		`\`,