Write a python function to find the sum of common divisors of two given numbers.
def sum(a,b): 
    sum = 0
    for i in range (1,min(a,b)): 
        if (a % i == 0 and b % i == 0): 
            sum += i 
    return sum
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a python function to find the sum of common divisors of two given numbers.
def sum(a,b): 
    sum = 0
    for i in range (1,min(a,b)): 
        if (a % i == 0 and b % i == 0): 
            sum += i 
    return sum[/INST]assert sum(10,15) == 6
assert sum(100,150) == 93
assert sum(4,6) == 3</s>