Testing mean#

Suppose you’re writing a function that computes the arithmetic mean (i.e., average, i.e., sum and divide by the length) of a list of numbers. You’d like to test your function. Which examples should you run?

Here is a sample you can run on IDLE:

>>> from example import mean

Please don't edit the line above---we need it for the code to work. Write as many doctests as you like for the function `mean` below.

Here's one to start you off:

>>> mean([1])
1.0

Consider using the following definitions of mean:

# Definition of mean that only returns the first element
def mean(l):
    return l[0]

# Definition of mean that only returns the last element
def mean(l):
    return l[-1]

# The correct definition
def mean(l):
    return sum(l) / len(l)

# Returns the median instead of the mean
def mean(l):
    l.sort()
    return float(l[len(l)//2])

Here are a few function calls you can use to test your function:

>>> mean([1,2,3])
2.0
>>> mean([3,1,2])
2.0
>>> mean([2,1])
1.5
>>> mean([1,2])
1.5

These tests ensure that the following events do not happen:

  • The function does not return the first element of the list

  • The function does not return the last element of the list

  • The function does not return the median of the list

It is important that all possible cases are concidered when making a function!