Lecture 7

Black Box and Glass Box Testing

With the below implementation, is the test set "n = 4 | n = -4 | n = 5" path complete?

def is_even(n):
    """ 
    Returns True if a number is even
    and False if not 
    """
    if n > 0 and n % 2 == 0:
        return True
    elif n < 0 and n % 2 == 0:
        return True
    else: 
        return False

Yes

With the above implementation, which value for n is incorrectly labeled by is_even?

n is very large (and positive)

n is very small (and negative)

n is 0

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Errors

Below is a piece of code and an error shown when running it. What is the problem?
```
L = 3
for i in range(len(L)):
    print(i)

ERROR MESSAGE:

 File "C:/Users/Ana/.spyder2-py3/temp.py", line 2, in 
    for i in range(len(L)):

TypeError: object of type 'int' has no len()
```
Exercise 3
 You are not allowed to name an integer with the variable name L

 range is not allowed to have an expression inside its parentheses

 You are not allowed to call len on an integer

 You are not allowed to print the loop variable i

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Exceptions

If the user enters "twenty" in the code below what does the program do?

try:
    n = int(input("How old are you? "))
    percent = round(n*100/80, 1)
    print("You've gone through", percent, "% of your life!")
except ValueError:
    print("Oops, must enter a number.")
except ZeroDivisionError:
    print("Division by zero.")
except:
    print("Something went very wrong.")