os: simplify TestRemoveAllDot

Use t.Chdir and t.TempDir to simplify test case code.

Change-Id: If4de06d2373100ce53a5b8f6702d5f4866e3b23d
Reviewed-on: https://go-review.googlesource.com/c/go/+/606897


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

src/os/removeall_test.go

@@ -187,30 +187,11 @@ func TestRemoveAllLongPath(t *testing.T) {
 }
 
 func TestRemoveAllDot(t *testing.T) {
-	prevDir, err := Getwd()
-	if err != nil {
-		t.Fatalf("Could not get wd: %s", err)
-	}
-	tempDir, err := MkdirTemp("", "TestRemoveAllDot-")
-	if err != nil {
-		t.Fatalf("Could not create TempDir: %s", err)
-	}
-	defer RemoveAll(tempDir)
+	t.Chdir(t.TempDir())
 
-	err = Chdir(tempDir)
-	if err != nil {
-		t.Fatalf("Could not chdir to tempdir: %s", err)
-	}
-
-	err = RemoveAll(".")
-	if err == nil {
+	if err := RemoveAll("."); err == nil {
 		t.Errorf("RemoveAll succeed to remove .")
 	}
-
-	err = Chdir(prevDir)
-	if err != nil {
-		t.Fatalf("Could not chdir %s: %s", prevDir, err)
-	}
 }
 
 func TestRemoveAllDotDot(t *testing.T) {