Python - doctest

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Demonstrating usage of doctest
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1. This doctest checks functionality of  python's plus operator.

>>> 2 + 4
6
>>> -10.5 + 8
-2.5

• Run the tests written in sample_tests.txt using the below command.

python3 ‑m doctest sample_tests.txt

• By default, no output is seen when all tests pass. To view a verbose output, use -v option as shown in below command.

python3 ‑m doctest -v sample_tests.txt

Output

Trying:
    2 + 4
Expecting:
    6
ok
Trying:
    -10.5 + 8
Expecting:
    -2.5
ok
1 items passed all tests:
   2 tests in sample_tests.txt
2 tests in 1 items.
2 passed and 0 failed.
Test passed.

2. The below doctest checks functionality of add2num function

>>> def add2num(x, y):
...       "This function returns sum of two numbers."
...       return x + y
>>> add2num(6, 7)
13
>>> add2num(-8.5, 7)
-1.5

• Using docstring

def add2num(x, y):
    """Adds two given numbers and returns the sum.
    >>> add2num(6, 7)
    13
    >>> add2num(-8.5, 7)
    -1.5
    """
    return x + y

python3 ‑m doctest sample_module.py

• Since all tests pass, you see an empty output.

3. This doctest checks functionality of insertlines function
>>> def insertlines(n):
...    print('Start')
...    for i in range(n):
...        print()
...    print('End')
>>> insertlines(2)
Start
<BLANKLINE>
<BLANKLINE>
End