os: add tests for UserCacheDir and UserConfigDir

Adds basic test scenarios for UserCacheDir and
UserConfigDir.

Fixes golang#57638

Change-Id: Ieb86e95faff44287bfa13daa0cb26e7b5401373b
Reviewed-on: https://go-review.googlesource.com/c/go/+/520262
Run-TryBot: Bryan Mills <[email protected]>
TryBot-Bypass: Bryan Mills <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>
Reviewed-by: Bryan Mills <[email protected]>
Auto-Submit: Bryan Mills <[email protected]>

Author: joshkraft

misc/go_android_exec/main.go

@@ -204,6 +204,7 @@ func runMain() (int, error) {
 		`; export GOPROXY=` + os.Getenv("GOPROXY") +
 		`; export GOCACHE="` + deviceRoot + `/gocache"` +
 		`; export PATH="` + deviceGoroot + `/bin":$PATH` +
+		`; export HOME="` + deviceRoot + `/home"` +
 		`; cd "` + deviceCwd + `"` +
 		"; '" + deviceBin + "' " + strings.Join(os.Args[2:], " ")
 	code, err := adbRun(cmd)

src/os/os_test.go

@@ -2823,6 +2823,53 @@ func TestDoubleCloseError(t *testing.T) {
 	t.Run("dir", testDoubleCloseError(sfdir))
 }
 
+func TestUserCacheDir(t *testing.T) {
+	t.Parallel()
+
+	dir, err := UserCacheDir()
+	if err != nil {
+		t.Skipf("skipping: %v", err)
+	}
+	if dir == "" {
+		t.Fatalf("UserCacheDir returned %q; want non-empty path or error", dir)
+	}
+
+	if err := MkdirAll(dir, 0777); err != nil {
+		t.Fatalf("could not create UserCacheDir: %v", err)
+	}
+	d, err := MkdirTemp(dir, "TestUserCacheDir")
+	if err != nil {
+		t.Fatalf("could not create a directory in UserCacheDir: %v", err)
+	}
+	if err := Remove(d); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestUserConfigDir(t *testing.T) {
+	t.Parallel()
+
+	dir, err := UserConfigDir()
+	if err != nil {
+		t.Skipf("skipping: %v", err)
+	}
+	if dir == "" {
+		t.Fatalf("UserConfigDir returned %q; want non-empty path or error", dir)
+	}
+
+	if err := MkdirAll(dir, 0777); err != nil {
+		t.Fatalf("could not create UserConfigDir: %v", err)
+	}
+
+	d, err := MkdirTemp(dir, "TestUserConfigDir")
+	if err != nil {
+		t.Fatalf("could not create a directory in UserConfigDir: %v", err)
+	}
+	if err := Remove(d); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestUserHomeDir(t *testing.T) {
 	t.Parallel()