public void ChangePasswordTest()
{
User user1 = new User();
user1.Name = "Jan";
user1.Surname = "Novák";
user1.ChangePassword("Nové heslo 123456987");
Assert.IsFalse(user1.CheckPassword("špatné heslo"));
Assert.IsTrue(user1.CheckPassword("Nové heslo 123456987"));
}