public void DirectorySecurity_CreateDirectory_NullSecurity()
        {
            DirectorySecurity security = null;
            string            path     = "whatever";

            Assert.Throws <ArgumentNullException>("directorySecurity", () => security.CreateDirectory(path));
            Assert.Throws <ArgumentNullException>("directorySecurity", () => FileSystemAclExtensions.CreateDirectory(security, path));
        }