"""
Ex 3.7 from "A primer on...
Write a function to evaluate a sum, and
then a test function to test this function. 
"""

#a)
def sum_1k(M):
    s = 0
    for k in range(1, M+1):
        s += 1 / k
    return s    

#b)
def test_sum_1k():
    M = 3
    tol = 1e-15
    #value for M = 3, calculated by hand:
    expected = 11 / 6
    computed = sum_1k(M)
    assert abs(expected - computed) < tol

test_sum_1k()

"""
Terminal> python sum_func.py
(No output if the test passes)
"""