os/exec: parallelize more tests

This cuts the wall duration for 'go test os/exec' and
'go test -race os/exec' roughly in half on my machine,
which is an even more significant speedup with a high '-count'.

For better or for worse, it may also increase the repro rate
of #34988.

Tests that use Setenv or Chdir or check for FDs opened during the test
still cannot be parallelized, but they are only a few of those.

Change-Id: I8d284d8bff05787853f825ef144aeb7a4126847f
Reviewed-on: https://go-review.googlesource.com/c/go/+/439196
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>

1 files changed, 26 insertions, 6 deletions

diff --git a/src/os/exec/lp_windows_test.go b/src/os/exec/lp_windows_test.go
index 1f609fffd0..d797b6c53c 100644
--- a/src/os/exec/lp_windows_test.go
+++ b/src/os/exec/lp_windows_test.go
@@ -334,12 +334,21 @@ var lookPathTests = []lookPathTest{
 }
 
 func TestLookPathWindows(t *testing.T) {
+	if testing.Short() {
+		maySkipHelperCommand("lookpath")
+		t.Skipf("skipping test in short mode that would build a helper binary")
+	}
+	t.Parallel()
+
 	tmp := t.TempDir()
 	printpathExe := buildPrintPathExe(t, tmp)
 
 	// Run all tests.
 	for i, test := range lookPathTests {
+		i, test := i, test
 		t.Run(fmt.Sprint(i), func(t *testing.T) {
+			t.Parallel()
+
 			dir := filepath.Join(tmp, "d"+strconv.Itoa(i))
 			err := os.Mkdir(dir, 0700)
 			if err != nil {
@@ -524,17 +533,28 @@ var commandTests = []commandTest{
 }
 
 func TestCommand(t *testing.T) {
+	if testing.Short() {
+		maySkipHelperCommand("exec")
+		t.Skipf("skipping test in short mode that would build a helper binary")
+	}
+	t.Parallel()
+
 	tmp := t.TempDir()
 	printpathExe := buildPrintPathExe(t, tmp)
 
 	// Run all tests.
 	for i, test := range commandTests {
-		dir := filepath.Join(tmp, "d"+strconv.Itoa(i))
-		err := os.Mkdir(dir, 0700)
-		if err != nil {
-			t.Fatal("Mkdir failed: ", err)
-		}
-		test.run(t, dir, printpathExe)
+		i, test := i, test
+		t.Run(fmt.Sprint(i), func(t *testing.T) {
+			t.Parallel()
+
+			dir := filepath.Join(tmp, "d"+strconv.Itoa(i))
+			err := os.Mkdir(dir, 0700)
+			if err != nil {
+				t.Fatal("Mkdir failed: ", err)
+			}
+			test.run(t, dir, printpathExe)
+		})
 	}
 }