问用JUnit实现两个变量互换的测试方法

EN

public void swap(int[] a, int[] b) {
    a[0] ^= b[0];
    b[0] = a[0] ^ b[0];
    a[0] = a[0] ^ b[0];
}

public void swap(int a, int b) {
    a ^= b;
    b = a ^ b;
    a = a ^ b;
}

public void swap(int[] a, int[] b) {
    a[0] ^= b[0];
    b[0] = a[0] ^ b[0];
    a[0] = a[0] ^ b[0];
}

public void swap(int[] a, int[] b) {
    if (a == b) { //do not swap 
        return;
    }

    if (a ==null) {
        return;
    }

    if (b ==null) {
        return;
    }

    a[0] ^= b[0];
    b[0] = a[0] ^ b[0];
    a[0] = a[0] ^ b[0];
}

//both a[0] and b[0] are different values
int[] a = {4};
int[] b = {5};

int copy_a = a[0];
int copy_b = b[0];

swap(a, b);

assertEquals("copy_a should be b[0]", copy_a, b[0]);
assertEquals("copy_b should be a[0]", copy_b, a[0]);

//both a[0] and b[0] are same values
a[0] = 4;
b[0] = 4;

copy_a = a[0];
copy_b = b[0];

swap(a, b);

assertEquals("copy_a should be copy_b", copy_a == copy_b, a[0] == b[0]);

//case when you pass same array as both arguments.

a[0] = 9;
copy_a = a[0];
swap(a, a);
assertEquals("copy_a should be a[0]", copy_a, a[0]);