Unit-Test : Compare Expected Result with hexadezimal

I want to compare a hexadecimal with a hexadecimal and show if its the same. For Example:

decimal = 255 
ExpResult = FF 
Hex[x] = FF --> true

//The part above ist the converterpart (dec in hex)

void decimalinhexadecimal(int t, int decimal , char ExpResult  ) // 
{
long int num;
int i = 1, x, y;
char hexa[100];
num = decimal;
while (num != 0) {
    y = num % 16;
    if (y < 10)
        y = y + 48; 
    else
        y = y + 55;
    hexa[i++] = y;
    num = num / 16;
}
printf("Hexadecimal:" );
for (x = i - 1; x> 0; x--)
    printf("%c", hexa[x]);

// This One is the test part
if (t >= 1)
{
    if (ExpResult != hexa[x]) // this one didnt work
    {
        printf("\n");
        printf("Error no hex\n");
    }
    else
    {
        printf("\n");
        printf("Erfolg!\n");
    }
}
else
{
    return;
}

}