Find the xor of numbers which appear twice

#[test]
fn t1() {
    let start = std::time::Instant::now();
    let val = Solution::duplicate_numbers_xor(vec![1, 2, 1, 3]);
    let expected = 1;
    log_result!(val == expected, "t1", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t2() {
    let start = std::time::Instant::now();
    let val = Solution::duplicate_numbers_xor(vec![1, 2, 3]);
    let expected = 0;
    log_result!(val == expected, "t2", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t3() {
    let start = std::time::Instant::now();
    let val = Solution::duplicate_numbers_xor(vec![1, 2, 2, 1]);
    let expected = 3;
    log_result!(val == expected, "t3", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t4() {
    let start = std::time::Instant::now();
    let val = Solution::duplicate_numbers_xor(vec![5, 5]);
    let expected = 5;
    log_result!(val == expected, "t4", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t5() {
    let start = std::time::Instant::now();
    let val = Solution::duplicate_numbers_xor(vec![1, 1, 2, 2, 3]);
    let expected = 3;
    log_result!(val == expected, "t5", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t6() {
    let start = std::time::Instant::now();
    let val = Solution::duplicate_numbers_xor(vec![50, 50]);
    let expected = 50;
    log_result!(val == expected, "t6", start, &expected, &val);
    assert_eq!(val, expected);
}

#[test]
fn t7() {
    let start = std::time::Instant::now();
    let val = Solution::duplicate_numbers_xor(vec![10, 20, 30]);
    let expected = 0;
    log_result!(val == expected, "t7", start, &expected, &val);
    assert_eq!(val, expected);
}