Write a python function to find the sum of even numbers at even positions.
def sum_even_and_even_index(arr,n):  
    i = 0
    sum = 0
    for i in range(0,n,2): 
        if (arr[i] % 2 == 0) : 
            sum += arr[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 even numbers at even positions.
def sum_even_and_even_index(arr,n):  
    i = 0
    sum = 0
    for i in range(0,n,2): 
        if (arr[i] % 2 == 0) : 
            sum += arr[i]  
    return sum[/INST]assert sum_even_and_even_index([5, 6, 12, 1, 18, 8],6) == 30
assert sum_even_and_even_index([3, 20, 17, 9, 2, 10, 18, 13, 6, 18],10) == 26
assert sum_even_and_even_index([5, 6, 12, 1],4) == 12</s>