Doctest#

The Python module doctest checks whether the tests specified in a docstring are fulfilled.

  1. In arithmetic.py you can add the following docstring:

     9def divide(x, y):
10    """Divides the first parameter by the second
11    >>> x, y, z = 7, -6.0, 0
12    >>> divide(x, y)
13    -1.1666666666666667
14    >>> divide(x, z)
15    Traceback (most recent call last):
16      File "<stdin>", line 1, in <module>
17    ZeroDivisionError: division by zero
18    """

  2. Then you can test it with:

    $ python -m doctest test/arithmetic.py -v
Trying:
    add(7,6)
Expecting:
    13
ok
Trying:
    x, y, z = 7, -6.0, 0
Expecting nothing
ok
Trying:
    divide(x, y)
Expecting:
    -1.1666666666666667
ok
Trying:
    divide(x, z)
Expecting:
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    ZeroDivisionError: division by zero
ok
Trying:
    multiply(7,6)
Expecting:
    42
ok
Trying:
    subtract(7,6)
Expecting:
    1
ok
1 items had no tests:
    arithmetic
4 items passed all tests:
   1 tests in arithmetic.add
   3 tests in arithmetic.divide
   1 tests in arithmetic.multiply
   1 tests in arithmetic.subtract
6 tests in 5 items.
6 passed and 0 failed.
Test passed.

    C:> Scripts\python -m doctest arithmetic.py -v
Trying:
    add(7,6)
Expecting:
    13
ok
Trying:
    x, y, z = 7, -6.0, 0
Expecting nothing
ok
Trying:
    divide(x, y)
Expecting:
    -1.1666666666666667
ok
Trying:
    divide(x, z)
Expecting:
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    ZeroDivisionError: division by zero
ok
Trying:
    multiply(7,6)
Expecting:
    42
ok
Trying:
    subtract(7,6)
Expecting:
    1
ok
1 items had no tests:
    arithmetic
4 items passed all tests:
   1 tests in arithmetic.add
   3 tests in arithmetic.divide
   1 tests in arithmetic.multiply
   1 tests in arithmetic.subtract
6 tests in 5 items.
6 passed and 0 failed.
Test passed.

  3. So that the doctests can also be imported into other modules, you should add the following lines:

    38if __name__ == "__main__":
39    import doctest
40
41    doctest.testmod(verbose=True)