os: simplify TestRemoveAllLongPath

Simplify the test logic by using t.TempDir, t.Chdir, and Chdir to
startPath parent.

Change-Id: Ibe71a8c26b8e54c22eb93510037605b69c67bc7a
Reviewed-on: https://go-review.googlesource.com/c/go/+/606896


LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/os/removeall_test.go

@@ -159,40 +159,25 @@ func TestRemoveAllLongPath(t *testing.T) {
 		t.Skip("skipping for not implemented platforms")
 	}
 
-	prevDir, err := Getwd()
-	if err != nil {
-		t.Fatalf("Could not get wd: %s", err)
-	}
+	startPath := t.TempDir()
+	t.Chdir(startPath)
 
-	startPath, err := MkdirTemp("", "TestRemoveAllLongPath-")
-	if err != nil {
-		t.Fatalf("Could not create TempDir: %s", err)
-	}
-	defer RemoveAll(startPath)
-
-	err = Chdir(startPath)
-	if err != nil {
-		t.Fatalf("Could not chdir %s: %s", startPath, err)
-	}
-
-	// Removing paths with over 4096 chars commonly fails
+	// Removing paths with over 4096 chars commonly fails.
+	name := strings.Repeat("a", 100)
 	for i := 0; i < 41; i++ {
-		name := strings.Repeat("a", 100)
-
-		err = Mkdir(name, 0755)
-		if err != nil {
+		if err := Mkdir(name, 0755); err != nil {
 			t.Fatalf("Could not mkdir %s: %s", name, err)
 		}
-
-		err = Chdir(name)
-		if err != nil {
+		if err := Chdir(name); err != nil {
 			t.Fatalf("Could not chdir %s: %s", name, err)
 		}
 	}
 
-	err = Chdir(prevDir)
+	// Chdir out of startPath before attempting to remove it,
+	// otherwise RemoveAll fails on aix, illumos and solaris.
+	err := Chdir(filepath.Join(startPath, ".."))
 	if err != nil {
-		t.Fatalf("Could not chdir %s: %s", prevDir, err)
+		t.Fatalf("Could not chdir: %s", err)
 	}
 
 	err = RemoveAll(startPath)