internal/mod/zip: make all tests parallel

I'm not sure why x/mod/zip only makes the sub-tests parallel.
Two of these tests deal with very large zip files,
but they don't create those large files in in-memory buffers;
the Create test writes to io.Discard, and Unzip uses temporary files.

Moreover, their subtests were already parallel, so we were already
creating multiple such large files at once anyway.

This helps slightly with `go test`, dropping from 2.9s to 1.6s
while CPU usage increases from 150% to 280% on my laptop.
The real difference is with `go test -race`, which we use in CI:
I see a drop from 80s to 43s, again using multiple CPUs better.

Signed-off-by: Daniel Martí <[email protected]>
Change-Id: I92cd8828ae2b11a7b83568c6145e020e3b54d754
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1170018
Unity-Result: CUE porcuepine <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Roger Peppe <[email protected]>

internal/mod/zip/zip_test.go

@@ -202,6 +202,7 @@ func formatCheckedFiles(cf modzip.CheckedFiles) string {
 }
 
 func TestCheckFilesWithDirWithTrailingSlash(t *testing.T) {
+	t.Parallel()
 	// When checking a zip file,
 	files := []fakeFile{{
 		name:  "cue.mod/",
@@ -221,6 +222,7 @@ func TestCheckFilesWithDirWithTrailingSlash(t *testing.T) {
 // focuses on how multiple errors and omissions are reported, rather than trying
 // to cover every case.
 func TestCheckFiles(t *testing.T) {
+	t.Parallel()
 	testPaths, err := filepath.Glob(filepath.FromSlash("testdata/check_files/*.txt"))
 	if err != nil {
 		t.Fatal(err)
@@ -274,6 +276,7 @@ func TestCheckFiles(t *testing.T) {
 // test focuses on how multiple errors and omissions are reported, rather than
 // trying to cover every case.
 func TestCheckDir(t *testing.T) {
+	t.Parallel()
 	testPaths, err := filepath.Glob(filepath.FromSlash("testdata/check_dir/*.txt"))
 	if err != nil {
 		t.Fatal(err)
@@ -324,6 +327,7 @@ func TestCheckDir(t *testing.T) {
 // covered by TestUnzip, so this test focuses on how multiple errors are
 // reported, rather than trying to cover every case.
 func TestCheckZip(t *testing.T) {
+	t.Parallel()
 	testPaths, err := filepath.Glob(filepath.FromSlash("testdata/check_zip/*.txt"))
 	if err != nil {
 		t.Fatal(err)
@@ -373,6 +377,7 @@ func TestCheckZip(t *testing.T) {
 }
 
 func TestCreate(t *testing.T) {
+	t.Parallel()
 	testDir := filepath.FromSlash("testdata/create")
 	testInfos, err := os.ReadDir(testDir)
 	if err != nil {
@@ -458,6 +463,7 @@ func shouldExclude(f *zip.File) bool {
 }
 
 func TestCreateFromDir(t *testing.T) {
+	t.Parallel()
 	testDir := filepath.FromSlash("testdata/create_from_dir")
 	testInfos, err := os.ReadDir(testDir)
 	if err != nil {
@@ -513,6 +519,7 @@ func TestCreateFromDir(t *testing.T) {
 }
 
 func TestCreateFromDirSpecial(t *testing.T) {
+	t.Parallel()
 	for _, test := range []struct {
 		desc     string
 		setup    func(t *testing.T, tmpDir string) string
@@ -589,6 +596,7 @@ func TestCreateFromDirSpecial(t *testing.T) {
 }
 
 func TestUnzip(t *testing.T) {
+	t.Parallel()
 	testDir := filepath.FromSlash("testdata/unzip")
 	testInfos, err := os.ReadDir(testDir)
 	if err != nil {
@@ -714,6 +722,7 @@ func TestCreateSizeLimits(t *testing.T) {
 	if testing.Short() {
 		t.Skip("creating large files takes time")
 	}
+	t.Parallel()
 	tests := append(sizeLimitTests[:], sizeLimitTest{
 		// negative file size may happen when size is represented as uint64
 		// but is cast to int64, as is the case in zip files.
@@ -775,6 +784,7 @@ func TestUnzipSizeLimits(t *testing.T) {
 	if testing.Short() {
 		t.Skip("creating large files takes time")
 	}
+	t.Parallel()
 	for _, test := range sizeLimitTests {
 		test := test
 		t.Run(test.desc, func(t *testing.T) {
@@ -842,6 +852,7 @@ func TestUnzipSizeLimitsSpecial(t *testing.T) {
 		t.Skip("skipping test; creating large files takes time")
 	}
 
+	t.Parallel()
 	for _, test := range []struct {
 		desc     string
 		wantErr  string