`/`,
		`\`,
	}

	for _, test := range tests {
		dir, err := os.Open(test)
		if err != nil {
			t.Fatalf("Open(%q) failed: %v", test, err)
		}
		dir.Close()
	}
}

func testMkdirAllAtRoot(t *testing.T, root string) {
	// Create a unique-enough directory name in root.
	base := fmt.Sprintf("%s-%d", t.Name(), os.Getpid())
	path := filepath.Join(root, base)
	if err := os.MkdirAll(path, 0777); err != nil {